drm/amd/pm: Fix missing thermal throttler status

On aldebaran, when thermal throttling happens due to excessive GPU
temperature, the reason for throttling event is missed in warning
message. This patch fixes it.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>