[NET]: Annotate callers of csum_fold() in net/*

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 6eee716..0017ccb 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -932,7 +932,7 @@
 
 	switch (skb->ip_summed) {
 	case CHECKSUM_COMPLETE:
-		if (!(u16)csum_fold(skb->csum))
+		if (!csum_fold(skb->csum))
 			break;
 		/* fall through */
 	case CHECKSUM_NONE: