net: Ppp_async: semaphore cleanup

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 Miller <davem@davemloft.net>
LKML-Reference: <20100907125055.460765783@linutronix.de>