Bug: [chassisd] "unknown" is also recorded as NPU kernel crash

[chartsai-nvidia]

Is it platform specific

generic

Importance or Severity

Critical

Description of the bug

"unknown" is also showed as "NPU kernel crash" in the log

Steps to Reproduce

NPU first boot

Actual Behavior and Expected Behavior

Actual behavior: shows kernel crash
Expected Behavior: should show correct last NPU reboot cause

Relevant log output

pmon#chassisd: NPU kernel crash detected from /host/reboot-cause/reboot-cause.txt; will power-cycle all admin-up DPUs

Output of show version, show techsupport

Attach files (if any)

No response

[chartsai-nvidia]

Should be fixed in this PR: sonic-net/sonic-platform-daemons#829