drm/amdkfd: Fix checkpoint-restore on multi-xcc

GPUs with multi-xcc have multiple MQDs per queue. This patch saves and
restores all the MQDs within the partition.

Signed-off-by: David Yat Sin <David.YatSin@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit a578f2a5)
Cc: stable@vger.kernel.org