[IPV4] UDP,UDPLITE: Sparse: {__udp4_lib,udp,udplite}_err() are of void.

Fix following sparse warnings:
| net/ipv4/udp.c:421:2: warning: returning void-valued expression
| net/ipv4/udplite.c:38:2: warning: returning void-valued expression
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

net/ipv4/udp.c

@@ -418,7 +418,7 @@ out:
 
 void udp_err(struct sk_buff *skb, u32 info)
 {
-	return __udp4_lib_err(skb, info, udp_hash);
+	__udp4_lib_err(skb, info, udp_hash);
 }
 
 /*

net/ipv4/udplite.c

@@ -35,7 +35,7 @@ static int udplite_rcv(struct sk_buff *skb)
 
 static void udplite_err(struct sk_buff *skb, u32 info)
 {
-	return __udp4_lib_err(skb, info, udplite_hash);
+	__udp4_lib_err(skb, info, udplite_hash);
 }
 
 static	struct net_protocol udplite_protocol = {