drm/amd/pm: optimize the interface for dpm feature status query

Drop extra CMN2ASIC_MAPPING_FEATURE transform. Also some cosmetic
fixes for better readability.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>