drm/ttm: fix dma_fence refcount imbalance on error path

the ttm_bo_add_move_fence takes a reference to the struct dma_fence, but
failed to release it on the error path, leading to a memory leak.
add dma_fence_put before return when error occur.

Signed-off-by: Lin Yi <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/ttm/ttm_bo.c

···
 		reservation_object_add_shared_fence(bo->resv, fence);
 
 		ret = reservation_object_reserve_shared(bo->resv, 1);
-		if (unlikely(ret))
+		if (unlikely(ret)) {
+			dma_fence_put(fence);
 			return ret;
+		}
 
 		dma_fence_put(bo->moving);
 		bo->moving = fence;