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

Get rid of init_MUTEX[_LOCKED]() and use sema_init() instead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: "David S. Miller" <davem@davemloft.net>
LKML-Reference: <20100907125055.557578360@linutronix.de>