staging: wilc1000: Remove semaphore close_exit_sync

The semaphore 'close_exit_sync' does not serve any purpose other
than delaying the deregistration of the device which it is trying
to protect from shared access. 'up' is called only when a subdevice
is closed and not when it is opened. So, the semaphore count only
goes up when the device is used.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>