drm/radeon: fix lockup when BOs aren't part of the VM on release

[ Upstream commit 26d4d129 ]

If we unmap BOs before releasing them them the intervall tree locks
up because we try to remove an entry not inside the tree.

Based on a patch from Michel Dänzer.
Signed-off-by: Christian König <christian.koenig@amd.com>
CC: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

drivers/gpu/drm/radeon/radeon_vm.c

@@ -1058,6 +1058,7 @@ void radeon_vm_bo_rmv(struct radeon_device *rdev,
 	list_del(&bo_va->bo_list);
 
 	mutex_lock(&vm->mutex);
+	if (bo_va->it.start || bo_va->it.last)
 		interval_tree_remove(&bo_va->it, &vm->va);
 	list_del(&bo_va->vm_status);