drm/amdgpu:implement CE/DE meta-init routines

those package need to insert into ring buffer for
SRIOV case. they are used to let CP do preemption.

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>