drm/amdgpu/userq: pin mqd and fw object bo to avoid eviction

drm/amdgpu/userq: pin mqd and fw object bo to avoid eviction

mqd and fw objects are queue core objects which should remain
valid and never be unmapped and evicted for user queues to work
properly.

During eviction if these buffers are evicted the hw continue to
use the invalid addresses and caused page faults and system hung.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit a3bbf32a336939a1d21b9561f8e53333b684b7ef)