RDMA/mlx5: Initialize return variable in case pagefault was skipped

Pagefaults occurred in non-ODP MR are completely valid events, so
initialize return variable to 0.

Fixes: 4d5422a3 ("IB/mlx5: Skip non-ODP MR when handling a page fault")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/odp.c

@@ -679,6 +679,7 @@ static int pagefault_single_data_segment(struct mlx5_ib_dev *dev,
 				    key);
 			if (bytes_mapped)
 				*bytes_mapped += bcnt;
+			ret = 0;
 			goto srcu_unlock;
 		}