[NET]: Annotate callers of the reset of checksum.h stuff.

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 2bf54ad..476cb60 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -877,7 +877,7 @@
 		}
 		if (tunnel->parms.o_flags&GRE_CSUM) {
 			*ptr = 0;
-			*(__be16*)ptr = ip_compute_csum((void*)(iph+1), skb->len - sizeof(struct iphdr));
+			*(__sum16*)ptr = ip_compute_csum((void*)(iph+1), skb->len - sizeof(struct iphdr));
 		}
 	}