Add atomic queue_refcount to struct bo_va, return -EBUSY to fail unmap
BO from the GPU if the bo_va queue_refcount is not zero.

Create queue to increase the bo_va queue_refcount, destroy queue to
decrease the bo_va queue_refcount, to ensure the queue buffers mapped on
the GPU when queue is active.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>