staging: wilc1000: wlan_initialize_threads: change argument with net_device

This patch changes function argument with net_device and use netdev private
data member wilc instead of g_linux_wlan. And there are assignment code with
different value continuously. Take last code.

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