sonypi: use mutex instead of semaphore

the Sony Programmable I/O Control 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: Mattia Dongili <malattia@linux.it>
Signed-off-by: Len Brown <len.brown@intel.com>