staging: wilc1000: remove unused semaphore and it's related codes

Variable rxq_event, rxq_wait_event and rxq_wait have the same pointer.

nwi->os_context.rxq_wait_event = (void *)&g_linux_wlan->rxq_event;
g_wlan.rxq_wait = inp->os_context.rxq_wait_event;

They are never aquired(down) since down function was only called in
linux_wlan_rxq_task which was deleted in a previous patch.
So delete variable rxq_event, rxq_wait_event, rxq_wait and it's related codes.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>