tty_ldisc: simplify tty_ldisc_autoload initialization

We have got existing macro to check for CONFIG option, use it.
Signed-off-by: Pavel Machek <pavel@denx.de>

Link: https://lore.kernel.org/r/20190924083244.GA4344@amdSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_ldisc.c

@@ -156,12 +156,7 @@ static void put_ldops(struct tty_ldisc_ops *ldops)
  *		takes tty_ldiscs_lock to guard against ldisc races
  */
 
-#if defined(CONFIG_LDISC_AUTOLOAD)
-	#define INITIAL_AUTOLOAD_STATE	1
-#else
-	#define INITIAL_AUTOLOAD_STATE	0
-#endif
-static int tty_ldisc_autoload = INITIAL_AUTOLOAD_STATE;
+static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD);
 
 static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
 {