ip: stash a pointer to msghdr in struct ping_fakehdr

... instead of storing its ->mgs_iter.iov there

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index 2d314837..bd46f73 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -163,8 +163,7 @@
 	pfh.icmph.checksum = 0;
 	pfh.icmph.un.echo.id = inet->inet_sport;
 	pfh.icmph.un.echo.sequence = user_icmph.icmp6_sequence;
-	/* XXX: stripping const */
-	pfh.iov = (struct iovec *)msg->msg_iter.iov;
+	pfh.msg = msg;
 	pfh.wcheck = 0;
 	pfh.family = AF_INET6;