staging: wilc1000: add wilc to netdev private data structure

This patch add wilc to struct perInterface_wlan_t which is netdev private
data to access wilc via netdev_priv function. Assign wilc to nic->wilc.
The global variable g_linux_wlan will be replaced with netdev private data
member wilc step by step.

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>