hamradio: 6pack: semaphore cleanup

The usage of this "mutex" is non obvious and probably a completion in
some places. Make it a semaphore.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Miller <davem@davemloft.net>

drivers/net/hamradio/6pack.c

@@ -606,7 +606,7 @@ static int sixpack_open(struct tty_struct *tty)
 
 	spin_lock_init(&sp->lock);
 	atomic_set(&sp->refcnt, 1);
-	init_MUTEX_LOCKED(&sp->dead_sem);
+	semaphore_init_locked(&sp->dead_sem);
 
 	/* !!! length of the buffers. MTU is IP MTU, not PACLEN!  */