[IPV6]: Improve readability in ip6_flowlabel.c

Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@redhat.com>

net/ipv6/ip6_flowlabel.c

@@ -538,7 +538,8 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
 
 		/* Do not check for fault */
 		if (!freq.flr_label)
-			copy_to_user(optval + ((u8*)&freq.flr_label - (u8*)&freq), &fl->label, sizeof(fl->label));
+			copy_to_user(&((struct in6_flowlabel_req __user *) optval)->flr_label,
+				     &fl->label, sizeof(fl->label));
 
 		sfl1->fl = fl;
 		sfl1->next = np->ipv6_fl_list;