[UDP]: Make full use of proto.h.udp_hash innovation.

After this we have only udp_lib_get_port to get the port and two 
stubs for ipv4 and ipv6. No difference in udp and udplite except
for initialized h.udp_hash member.

I tried to find a graceful way to drop the only difference between
udp_v4_get_port and udp_v6_get_port (i.e. the rcv_saddr comparison 
routine), but adding one more callback on the struct proto didn't 
appear such :( Maybe later.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index b4cbdce..635940d 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -125,6 +125,8 @@
 	sk_common_release(sk);
 }
 
+extern int	udp_lib_get_port(struct sock *sk, unsigned short snum,
+		int (*)(const struct sock*,const struct sock*));
 
 /* net/ipv4/udp.c */
 extern int	udp_get_port(struct sock *sk, unsigned short snum,