tty: Don't reenable already enabled ldisc

tty_ldisc_hangup() guarantees the ldisc is enabled (or that there
is no ldisc). Since __tty_hangup() was the only user, re-define
tty_ldisc_enable() in file-scope.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -693,7 +693,6 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
 	 */
 	set_bit(TTY_HUPPED, &tty->flags);
 	clear_bit(TTY_HUPPING, &tty->flags);
-	tty_ldisc_enable(tty);
 
 	tty_unlock(tty);
 

drivers/tty/tty_ldisc.c

@@ -373,7 +373,7 @@ static inline void tty_ldisc_put(struct tty_ldisc *ld)
  *	Clearing directly is allowed.
  */
 
-void tty_ldisc_enable(struct tty_struct *tty)
+static void tty_ldisc_enable(struct tty_struct *tty)
 {
 	clear_bit(TTY_LDISC_HALTED, &tty->flags);
 	set_bit(TTY_LDISC, &tty->flags);

include/linux/tty.h

@@ -561,8 +561,6 @@ extern void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty);
 extern void tty_ldisc_init(struct tty_struct *tty);
 extern void tty_ldisc_deinit(struct tty_struct *tty);
 extern void tty_ldisc_begin(void);
-/* This last one is just for the tty layer internals and shouldn't be used elsewhere */
-extern void tty_ldisc_enable(struct tty_struct *tty);
 
 
 /* n_tty.c */