drm/amdgpu: Add gmc interface to request NPS mode

Add a common interface in GMC to request NPS mode through PSP. Also add
a variable in hive and gmc control to track the last requested mode.

Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>