[NET]: Split skb->csum

... into anonymous union of __wsum and __u32 (csum and csum_offset resp.)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 07c25d6..a90bc43 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1414,7 +1414,7 @@
 					      skb->len - csstart, 0);
 
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
-		long csstuff = csstart + skb->csum;
+		long csstuff = csstart + skb->csum_offset;
 
 		*((__sum16 *)(to + csstuff)) = csum_fold(csum);
 	}