drivers/net: return operator cleanup

Change "return (EXPR);" to "return EXPR;"

return is not a function, parentheses are not required.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/mlx4/en_selftest.c b/drivers/net/mlx4/en_selftest.c
index 43357d3..9c91a92 100644
--- a/drivers/net/mlx4/en_selftest.c
+++ b/drivers/net/mlx4/en_selftest.c
@@ -107,7 +107,7 @@
 mlx4_en_test_loopback_exit:
 
 	priv->validate_loopback = 0;
-	return (!loopback_ok);
+	return !loopback_ok;
 }