net/mlx4_en: Fix build break when CONFIG_INET is off

MLX4_EN depends on NETDEVICES, ETHERNET and INET Kconfigs.
Make sure they are listed in MLX4_EN Kconfig dependencies.

This fixes the following build break:

drivers/net/ethernet/mellanox/mlx4/en_rx.c:582:18: warning: ‘struct iphdr’ declared inside parameter list [enabled by default]
struct iphdr *iph)
^
drivers/net/ethernet/mellanox/mlx4/en_rx.c:582:18: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]
drivers/net/ethernet/mellanox/mlx4/en_rx.c: In function ‘get_fixed_ipv4_csum’:
drivers/net/ethernet/mellanox/mlx4/en_rx.c:586:20: error: dereferencing pointer to incomplete type
_u8 ipproto = iph->protocol;

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/Kconfig

@@ -5,7 +5,7 @@
 config MLX4_EN
 	tristate "Mellanox Technologies 1/10/40Gbit Ethernet support"
 	depends on MAY_USE_DEVLINK
-	depends on PCI
+	depends on PCI && NETDEVICES && ETHERNET && INET
 	select MLX4_CORE
 	imply PTP_1588_CLOCK
 	---help---