tty_wakeup cleanup

- remove wake_up_interruptible(&tty->write_wait) surrounding
  tty_wakup(tty);
- substitute tty->ldisc.write_wakeup(tty) + wake_up() by tty_wakeup(tty);

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>