staging: wilc1000: fix comparison style of if statement in handle_get_ip_address

This patch changes conditional comparison of if statement as if (ret)
instead of using if (ret != 0)

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>