drm/amdgpu/gfx10: remap queue after reset successfully

Kiq command unmap_queues only does the dequeueing action.
We have to map the queue back with clean mqd.

v2: fix up error handling (Alex)

Acked-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Signed-off-by: Jiadong Zhu <Jiadong.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>