IB/mlx4: Fix an error handling path in 'mlx4_ib_rereg_user_mr()'

Before returning -EPERM we should release some resources, as already done
in the other error handling path of the function.

Fixes: d8f9cc32 ("IB/mlx4: Mark user MR as writable if actual virtual memory is writable")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx4/mr.c

@@ -486,8 +486,11 @@ int mlx4_ib_rereg_user_mr(struct ib_mr *mr, int flags,
 	}
 
 	if (flags & IB_MR_REREG_ACCESS) {
-		if (ib_access_writable(mr_access_flags) && !mmr->umem->writable)
-			return -EPERM;
+		if (ib_access_writable(mr_access_flags) &&
+		    !mmr->umem->writable) {
+			err = -EPERM;
+			goto release_mpt_entry;
+		}
 
 		err = mlx4_mr_hw_change_access(dev->dev, *pmpt_entry,
 					       convert_access(mr_access_flags));