drm/damdgpu:add new mqd member in ring

introduce a new mqd member in ring is for later usage.
we need keep a clean version of MQD for the purpose
of recovering compute rings from hang.

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