drm/amdgpu/umsch: don't execute umsch test when GPU is in reset/suspend

umsch test needs full GPU functionality(e.g., VM update, TLB flush,
possibly buffer moving under memory pressure) which may be not ready
under these states. Just skip it to avoid potential issues.

Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Veerabadhran Gopalakrishnan <Veerabadhran.Gopalakrishnan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>