tty: make tty_ldisc_ops::hangup return void

The documentation says that the return value of tty_ldisc_ops::hangup
hook is ignored. And it really is, so there is no point for its return
type to be int. Switch it to void and all the hooks too.

Cc: Dmitry Torokhov <[e-mail]>
Cc: Wolfgang Grandegger <[e-mail]>
Cc: Marc Kleine-Budde <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Liam Girdwood <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Jaroslav Kysela <[e-mail]>
Cc: Takashi Iwai <[e-mail]>
Cc: Peter Ujfalusi <[e-mail]>
Acked-by: Dmitry Torokhov <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Acked-by: Marc Kleine-Budde <[e-mail]>
Signed-off-by: Jiri Slaby <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/driver-api/serial/tty.rst

···
 hangup()		Called when the tty line is hung up.
 			The line discipline should cease I/O to the tty.
 			No further calls into the ldisc code will occur.
-			The return value is ignored. Can sleep.
+			Can sleep.
 
 read()			(optional) A process requests reading data from
 			the line. Multiple read calls may occur in parallel

drivers/input/serio/serport.c

···
 }
 #endif
 
-static int serport_ldisc_hangup(struct tty_struct *tty)
+static void serport_ldisc_hangup(struct tty_struct *tty)
 {
 	struct serport *serport = (struct serport *) tty->disc_data;
 	unsigned long flags;
···
 	spin_unlock_irqrestore(&serport->lock, flags);
 
 	wake_up_interruptible(&serport->wait);
-	return 0;
 }
 
 static void serport_ldisc_write_wakeup(struct tty_struct * tty)

drivers/net/can/slcan.c

···
 	/* This will complete via sl_free_netdev */
 }
 
-static int slcan_hangup(struct tty_struct *tty)
+static void slcan_hangup(struct tty_struct *tty)
 {
 	slcan_close(tty);
-	return 0;
 }
 
 /* Perform I/O control on an active SLCAN channel. */

drivers/net/ppp/ppp_async.c

···
  * Wait for I/O to driver to complete and unregister PPP channel.
  * This is already done by the close routine, so just call that.
  */
-static int ppp_asynctty_hangup(struct tty_struct *tty)
+static void ppp_asynctty_hangup(struct tty_struct *tty)
 {
 	ppp_asynctty_close(tty);
-	return 0;
 }
 
 /*

drivers/net/ppp/ppp_synctty.c

···
  * Wait for I/O to driver to complete and unregister PPP channel.
  * This is already done by the close routine, so just call that.
  */
-static int ppp_sync_hangup(struct tty_struct *tty)
+static void ppp_sync_hangup(struct tty_struct *tty)
 {
 	ppp_sync_close(tty);
-	return 0;
 }
 
 /*

drivers/net/slip/slip.c

···
 	/* This will complete via sl_free_netdev */
 }
 
-static int slip_hangup(struct tty_struct *tty)
+static void slip_hangup(struct tty_struct *tty)
 {
 	slip_close(tty);
-	return 0;
 }
  /************************************************************************
   *			STANDARD SLIP ENCAPSULATION		  	 *

include/linux/tty_ldisc.h

···
 	void	(*set_termios)(struct tty_struct *tty, struct ktermios *old);
 	__poll_t (*poll)(struct tty_struct *, struct file *,
 			     struct poll_table_struct *);
-	int	(*hangup)(struct tty_struct *tty);
+	void	(*hangup)(struct tty_struct *tty);
 
 	/*
 	 * The following routines are called from below.

sound/soc/codecs/cx20442.c

···
 }
 
 /* Line discipline .hangup() */
-static int v253_hangup(struct tty_struct *tty)
+static void v253_hangup(struct tty_struct *tty)
 {
 	v253_close(tty);
-	return 0;
 }
 
 /* Line discipline .receive_buf() */

sound/soc/ti/ams-delta.c

···
 }
 
 /* Line discipline .hangup() */
-static int cx81801_hangup(struct tty_struct *tty)
+static void cx81801_hangup(struct tty_struct *tty)
 {
 	cx81801_close(tty);
-	return 0;
 }
 
 /* Line discipline .receive_buf() */