The device could only check the checksum of TCP and UDP packets. Therefore,
for the IPv4 packets excluding TCP and UDP, the check of checksum is necessary,
even though the IP checksum is correct.

Take ICMP for example, The IP checksum may be correct, but the ICMP checksum
may be wrong.
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>