This moves and renames the AMDGPU scheduler to a common location in DRM
in order to facilitate re-use by other drivers. This is mostly a straight
forward rename with no code changes.

One notable exception is the function to_drm_sched_fence(), which is no
longer a inline header function to avoid the need to export the
drm_sched_fence_ops_scheduled and drm_sched_fence_ops_finished structures.
Reviewed-by: NChunming Zhou <david1.zhou@amd.com>
Tested-by: NDieter Nützel <Dieter@nuetzel-hh.de>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NLucas Stach <l.stach@pengutronix.de>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>