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/sctp/socket.c b/net/sctp/socket.c
index 0397ac9..c92f96cd 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1609,9 +1609,6 @@
 	__u16 sinfo_flags = 0;
 	long timeo;
 	int err;
-	struct iov_iter from;
-
-	iov_iter_init(&from, WRITE, msg->msg_iov, msg->msg_iovlen, msg_len);
 
 	err = 0;
 	sp = sctp_sk(sk);
@@ -1950,7 +1947,7 @@
 	}
 
 	/* Break the message into multiple chunks of maximum size. */
-	datamsg = sctp_datamsg_from_user(asoc, sinfo, &from);
+	datamsg = sctp_datamsg_from_user(asoc, sinfo, &msg->msg_iter);
 	if (IS_ERR(datamsg)) {
 		err = PTR_ERR(datamsg);
 		goto out_free;