[PATCH] mv643xx_eth: Request HW checksum generation only for IPv4
This patch removes the NETIF_F_HW_CSUM flag to be able to use other protocols
than IPv4. Hardware checksums for IPv4 should continue to work because
NETIF_F_IP_CSUM is still set. The sanity-check has been enhanced to check
the used protocol and to not access skb->iph for non-ipv4-packets.