drm/amdgpu: add amdgpu_gfx_sched_mask and amdgpu_compute_sched_mask debugfs

drm/amdgpu: add amdgpu_gfx_sched_mask and amdgpu_compute_sched_mask debugfs

compute/gfx may have multiple rings on some hardware.
In some cases, userspace wants to run jobs on a specific ring for validation purposes.
This debugfs entry helps to disable or enable submitting jobs to a specific ring.
This entry is populated only if there are at least two or more cores in the gfx/compute ip.

Signed-off-by: Jesse Zhang <[email protected]>
Suggested-by: Alex Deucher <[email protected]>
Reviewed-by: Tim Huang <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>