udp: move logic out of udp[46]_ufo_send_check

In udp[46]_ufo_send_check the UDP checksum initialized to the pseudo
header checksum. We can move this logic into udp[46]_ufo_fragment.
After this change udp[64]_ufo_send_check is a no-op.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/ipv4/udp_offload.c
Simple merge

diff --cc net/ipv6/udp_offload.c
Simple merge