staging: wilc1000: GetIfHandler: add argument struct wilc and use it

This patch adds new argument struct wilc and use it instead of
g_linux_wlan. And also pass wilc to the function.

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