Use mutex instead of semaphore in CAPI 2.0 driver

The CAPI 2.0 driver uses a semaphore as mutex.  Use the mutex API instead of
the (binary) semaphore.

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Acked-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>