[IPV6]: Clear up user copy warning in flowlabel code.

We are intentionally ignoring the copy_to_user() value,
make it clear to the compiler too.

Noted by Jeff Garzik.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6_flowlabel.c

@@ -535,10 +535,12 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
 		if (err)
 			goto done;
 
-		/* Do not check for fault */
-		if (!freq.flr_label)
-			copy_to_user(&((struct in6_flowlabel_req __user *) optval)->flr_label,
-				     &fl->label, sizeof(fl->label));
+		if (!freq.flr_label) {
+			if (copy_to_user(&((struct in6_flowlabel_req __user *) optval)->flr_label,
+					 &fl->label, sizeof(fl->label))) {
+				/* Intentionally ignore fault. */
+			}
+		}
 
 		sfl1->fl = fl;
 		sfl1->next = np->ipv6_fl_list;