drm/amd/pm: Add warning for unexpected PG requests

v1: Ideally power gate/ungate requests shouldn't come when smu block is
uninitialized. Add a WARN message to check the origins if such a thing
ever happens.

v2: Use dev_WARN to log device info (Felix/Guchun).

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Kevin Yang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>