USB: ELAN U132 Host Controller Driver: convert sw_lock to mutex

The ELAN U132 Host Controller Driver uses the semaphore sw_lock as
mutex. Use the mutex API instead of the (binary) semaphore.

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>