net: switch memcpy_fromiovec()/memcpy_fromiovecend() users to copy_from_iter()

That takes care of the majority of ->sendmsg() instances - most of them
via memcpy_to_msg() or assorted getfrag() callbacks.  One place where we
still keep memcpy_fromiovecend() is tipc - there we potentially read the
same data over and over; separate patch, that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/net/udplite.h

@@ -20,8 +20,7 @@ static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
 				      int len, int odd, struct sk_buff *skb)
 {
 	struct msghdr *msg = from;
-	/* XXX: stripping const */
-	return memcpy_fromiovecend(to, (struct iovec *)msg->msg_iter.iov, offset, len);
+	return copy_from_iter(to, len, &msg->msg_iter) != len ? -EFAULT : 0;
 }
 
 /* Designate sk as UDP-Lite socket */