drm/amdgpu: add the sched_score to amdgpu_ring_init

Allow separate ring to share the same scheduler score.

No functional change.

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