riscv: Add remaining module relocations

[xmzzz]

Backport the upstream RISC-V module relocation support to allow loading
kernel modules built with newer binutils (e.g. 2.42) that emit
R_RISCV_32_PCREL and other relocation types.

This fixes the "Unknown relocation type 57" error observed when loading
modules such as cambricon_drv compiled with newer toolchains.

Included patches:

1. Revert "sg2042: riscv: kernel: Optimize apply_relocate_add()"
2. riscv: Avoid unaligned access when relocating modules
3. riscv: Add remaining module relocations
4. RISC-V: Don't rely on positional structure initialization
5. riscv: Safely remove entries from relocation list
6. riscv: Correct type casting in module loading
7. riscv: module: Allocate PLT entries for R_RISCV_PLT32
8. riscv: Fix module loading free order
9. riscv: Correctly free relocation hashtable on error
10. riscv: Fix relocation hashtable size
11. riscv: module: remove relocation_head rel_entry member allocation
12. riscv: Use kvmalloc_array on relocation_hashtable

Test:

• Built a minimal test module (pcrel_test.ko) that forces generation of
  an R_RISCV_32_PCREL relocation. Verified with readelf:

  $ riscv64-unknown-linux-gnu-readelf -r pcrel_test.ko | grep 32_PCREL
  000000000000 003600000039 R_RISCV_32_PCREL 0000000000000000 pcrel_target + 0

• Loaded the module successfully on LicheePi 4A board.
  dmesg output:

$ sudo insmod ./pcrel_test.ko 
[sudo] password for openeuler: 
[  688.973056][ T1250] pcrel_test: loading out-of-tree module taints kernel.
[  688.979904][ T1250] pcrel_test: module verification failed: signature and/or required key missing - tainting kernel
[  688.991394][ T1250] R_RISCV_32_PCREL OK: value=0xffffdff8 expected=0xffffdff8

fix: #310

[github-actions]

---

开始测试 log: https://github.com/RVCK-Project/rvck/actions/runs/29353724774

参数解析结果

args	value
repository	RVCK-Project/rvck
head ref	pull/334/head
base ref	rvck-6.6
LAVA repo	RVCK-Project/lavaci
LAVA hardware	['qemu']
LAVA Testcase path	lava-testcases/common-test/ltp/ltp.yaml
need run job	kunit-test,kernel-build,check-patch,lava-trigger

---

测试完成

详细结果:

check	result
kunit-test	success
kernel-build	success
check-patch	success
lava-trigger-qemu	success
lava-trigger-sg2042	skipped
lava-trigger-k1	skipped
lava-trigger-lpi4a	skipped

Kunit Test Result

[17:30:17] Testing complete. Ran 482 tests: passed: 465, skipped: 17

• detail log: https://github.com/RVCK-Project/rvck/actions/runs/29353724774/attempts/1/#summary-87156080909

Kernel Build Result

• Kernel build succeeded: RVCK-Project/rvck/334_29353724774_1/

• 93d57dc650e5a4ecefd3d9bd35b9bf84 /srv/guix_result/d182f33f45680fba26dad1fa22bda13fbc401a76/Image

• f137279a02ca176b89c5506e96004049 /root/initramfs.img

• detail log: https://github.com/RVCK-Project/rvck/actions/runs/29353724774/attempts/1/#summary-87156080818

Check Patch Result

Total Errors	0
Total Warnings	23

• detail log: https://github.com/RVCK-Project/rvck/actions/runs/29353724774/attempts/1/#summary-87156080761

LAVA Check (qemu)

args	value
testcase_repo	RVCK-Project/lavaci
lava_template	lava-job-template/qemu/qemu-ltp.yaml
testcase_path	lava-testcases/common-test/ltp/ltp.yaml
kernel_download_url	http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck/334_29353724774_1/Image
initramfs_download_url	http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck/334_29353724774_1/initramfs.img
rootfs_download_url	https://fast-mirror.isrc.ac.cn/openeuler-sig-riscv/openEuler-RISC-V/RVCK/openEuler24.03-LTS-SP1/openeuler-rootfs.img.zst
testcase_ref	main
testitem_name	RVCK-Project_rvck_pull_request_target_334__common-test_qemu

result: Lava check done!

• lava log: https://lava.oerv.ac.cn/scheduler/job/3456

• lava result count: [pass]: 10

• detail log: https://github.com/RVCK-Project/rvck/actions/runs/29353724774/attempts/1/#summary-87188658109

[unicornx]

@xmzzz

Test:

• Built a minimal test module (pcrel_test.ko) that forces generation of
  an R_RISCV_32_PCREL relocation. Verified with readelf:

请问如何制作出这种 ko？对工具链和编译选项有何要求，我这里想试一下。

$ riscv64-unknown-linux-gnu-readelf -r pcrel_test.ko | grep 32_PCREL
000000000000 003600000039 R_RISCV_32_PCREL 0000000000000000 pcrel_target + 0

• Loaded the module successfully on LicheePi 4A board.

这个问题和硬件应该没有关系吧，我想基于 QEMU 测试一下，ok？

dmesg output:

$ sudo insmod ./pcrel_test.ko 
[sudo] password for openeuler: 
[  688.973056][ T1250] pcrel_test: loading out-of-tree module taints kernel.
[  688.979904][ T1250] pcrel_test: module verification failed: signature and/or required key missing - tainting kernel
[  688.991394][ T1250] R_RISCV_32_PCREL OK: value=0xffffdff8 expected=0xffffdff8

fix: #310