drm/amdgpu: stop trying to suspend UVD sessions v2

Saving the current UVD state on suspend and restoring it on resume
just doesn't work reliable. Just close cleanup all sessions on suspend.

Ported from radeon commit "12e49fea".

v2: rebased

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)