[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/ip_gre.c b/net/ipv4/ip_gre.c
index 2522114..2bf54ad 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -557,7 +557,7 @@
 	struct iphdr *iph;
 	u8     *h;
 	__be16    flags;
-	u16    csum = 0;
+	__sum16   csum = 0;
 	__be32 key = 0;
 	u32    seqno = 0;
 	struct ip_tunnel *tunnel;
@@ -580,7 +580,7 @@
 		if (flags&GRE_CSUM) {
 			switch (skb->ip_summed) {
 			case CHECKSUM_COMPLETE:
-				csum = (u16)csum_fold(skb->csum);
+				csum = csum_fold(skb->csum);
 				if (!csum)
 					break;
 				/* fall through */