Move IPv4-specific UDP bits from net/ipv4/udp.c into (new) net/ipv4/udp_ipv4.c.
Rename net/ipv4/udplite.c to net/ipv4/udplite_ipv4.c.
Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>