staging: wilc1000: use g_linux_wlan->rxq_cs for function arguemnt

Use mutex variable g_linux_wlan->rxq_cs instead of pointer varialbe.
No need to make extra pointer variable for the mutex. Remove
rxq_critical_section, rxq_lock and it's related codes.

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