MAINTAINERS: Update mlx4_en entry

Add Ido Shamay as co-maintainer for the mlx4 Ethernet driver.
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -6323,6 +6323,7 @@ F:	drivers/scsi/megaraid/
 
 MELLANOX ETHERNET DRIVER (mlx4_en)
 M:	Amir Vadai <amirv@mellanox.com>
+M:	Ido Shamay <idos@mellanox.com>
 L:	netdev@vger.kernel.org
 S:	Supported
 W:	http://www.mellanox.com