drm/amdgpu: change ring priority after pushing the job (v2)

Pushing a job can change the ring assignment of an entity.

v2: squash in:
"drm/amdgpu: fix job priority handling" (Christian)

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>