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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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);