net: fix IPv4 checksum
net: fix IPv4 checksum

0xffff is invalid for IPv4 checksum (RFC1624)

Fixes: 6006818cfb26 ("net: new checksum functions")
Cc: stable@dpdk.org

Signed-off-by: Hongzhi Guo <abe93f602be144090df070efae6a0f4b34f513f2@huawei.com>
Reviewed-by: Morten Brørup <77666125932addc6fc525b281b518fd8fd2203d8@smartsharesystems.com>
Acked-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk