pwm: th1520: use vertical import style

Convert `use` imports to vertical layout for better readability and
maintainability.

Signed-off-by: Guru Das Srinagesh <linux@gurudas.dev>
Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>

Author: Guru Das Srinagesh

drivers/pwm/pwm_th1520.rs

@@ -23,15 +23,21 @@
 use core::ops::Deref;
 use kernel::{
     clk::Clk,
-    device::{Bound, Core, Device},
+    device::{
+        Bound,
+        Core,
+        Device, //
+    },
     devres,
     io::{
         mem::IoMem,
         Io, //
     },
-    of, platform,
+    of,
+    platform, //
     prelude::*,
-    pwm, time,
+    pwm,
+    time, //
 };
 
 const TH1520_MAX_PWM_NUM: u32 = 6;