drm/amd: abstract kernel rq and normal rq to priority of run queue

drm/amd: abstract kernel rq and normal rq to priority of run queue

Allows us to set priorities in the scheduler.

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>