staging: wilc1000: init_irq: change argument and use netdev private wilc

This patch changes function argument type wilc with net_device and use
netdev private data member wilc instead of p_nic.

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>