sysdev: use mutex instead of semaphore

The sysdev code use a semaphore as mutex.  Use the mutex API instead of the
(binary) semaphore.

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>