put iov_iter into msghdr

Note that the code _using_ ->msg_iter at that point will be very
unhappy with anything other than unshifted iovec-backed iov_iter.
We still need to convert users to proper primitives.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 8dd4ae0..c0d82f7 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -811,7 +811,8 @@
 	pfh.icmph.checksum = 0;
 	pfh.icmph.un.echo.id = inet->inet_sport;
 	pfh.icmph.un.echo.sequence = user_icmph.un.echo.sequence;
-	pfh.iov = msg->msg_iov;
+	/* XXX: stripping const */
+	pfh.iov = (struct iovec *)msg->msg_iter.iov;
 	pfh.wcheck = 0;
 	pfh.family = AF_INET;