net: wan/cosa.c: Convert "mutex" to semaphore

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

drivers/net/wan/cosa.c

@@ -574,7 +574,7 @@ static int cosa_probe(int base, int irq, int dma)
 
 		/* Initialize the chardev data structures */
 		mutex_init(&chan->rlock);
-		init_MUTEX(&chan->wsem);
+		semaphore_init(&chan->wsem);
 
 		/* Register the network interface */
 		if (!(chan->netdev = alloc_hdlcdev(chan))) {