drm/amdgpu: separate the mqd_backup for kiq from kcq

This will benifit the mqd indexing for kiq/kcq in multi XCD case.

Signed-off-by: Le Ma <le.ma@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>