[NET]: Annotate checksums in on-the-wire packets.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 21dd569..6e7ea2f 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -30,7 +30,7 @@
 {
 	__u8 type;
 	__u8 code;		/* For newer IGMP */
-	__be16 csum;
+	__sum16 csum;
 	__be32 group;
 };