init: Support reboot reason with thermal warmreset

Thermal shutdown could be due to tskin temperature or
battery temperature. Pass reason while rebooting the
system to reflect properly in boot.reason

Bug: 238464124
Test: Build and boot on device. Check reboot reason
for thermal shutdown and battery thermal shutdown with
thermal warmreset enabled.

Change-Id: I192562fed48ae7da7843e383362cd22a76ce479f