drm/amdgpu: save and restore UVD context with suspend and resume

and revert fix following it accordingly

Revert "drm/amdgpu: stop trying to suspend UVD sessions v2"
Revert "drm/amdgpu: fix the UVD suspend sequence order"

Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>