drm/amdgpu: enable gfx wave limiting for high priority compute jobs

Enable gfx wave limiting for gfx jobs before pushing high priority
compute jobs so that high priority compute jobs gets more resources
to finish early.

v2: use ring priority instead of job priority.

Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>