tty: buffers: Move hidden buffer index advance into outer loop

The advance of the 'read' buffer index belongs in the outer
flip buffer consume loop, with the other buffer index arithmetic.

No functional change.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_buffer.c

@@ -444,7 +444,6 @@ receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
 		if (count)
 			disc->ops->receive_buf(tty, p, f, count);
 	}
-	head->read += count;
 	return count;
 }
 
@@ -506,6 +505,7 @@ static void flush_to_ldisc(struct work_struct *work)
 		count = receive_buf(tty, head, count);
 		if (!count)
 			break;
+		head->read += count;
 	}
 
 	mutex_unlock(&buf->lock);