mv643xx_eth: include linux/ip.h to fix build

mv643xx_eth uses ip_hdr() (defined in linux/ip.h), but relied on
another header file to include the needed header file indirectly.
In latest net-next this indirect include chain is gone, so the
driver fails to build.  Include linux/ip.h explicitly to fix this.
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mv643xx_eth.c

@@ -38,6 +38,7 @@
 #include <linux/init.h>
 #include <linux/dma-mapping.h>
 #include <linux/in.h>
+#include <linux/ip.h>
 #include <linux/tcp.h>
 #include <linux/udp.h>
 #include <linux/etherdevice.h>