cx20442: tty_ldisc_ops::write_wakeup is optional

TTY layer does nothing if tty_ldisc_ops::write_wakeup is NULL, so there
is no need to implement an empty one in cx20442. Drop it.

Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210722115141.516-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sound/soc/codecs/cx20442.c

@@ -279,19 +279,13 @@ static void v253_receive(struct tty_struct *tty, const unsigned char *cp,
 	}
 }
 
-/* Line discipline .write_wakeup() */
-static void v253_wakeup(struct tty_struct *tty)
-{
-}
-
 struct tty_ldisc_ops v253_ops = {
 	.name = "cx20442",
 	.owner = THIS_MODULE,
 	.open = v253_open,
 	.close = v253_close,
 	.hangup = v253_hangup,
 	.receive_buf = v253_receive,
-	.write_wakeup = v253_wakeup,
 };
 EXPORT_SYMBOL_GPL(v253_ops);