[IPV6]: Need to use pskb_trim_rcsum().

Fix pskb_trim usage in ipv6. Only the udp one is really
a bug, other places are just doing equivalent code.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 5be6da2..3b9fa90 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -459,11 +459,10 @@
 		IP6_INC_STATS_BH(IPSTATS_MIB_INTRUNCATEDPKTS);
 		goto drop;
 	}
-	if (pkt_len + sizeof(struct ipv6hdr) < skb->len) {
-		__pskb_trim(skb, pkt_len + sizeof(struct ipv6hdr));
-		if (skb->ip_summed == CHECKSUM_HW)
-			skb->ip_summed = CHECKSUM_NONE;
-	}
+
+	if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
+		goto drop;
+
 	return 1;
 
 drop: