broadcom-wl: support probe of 'wds' devices

'nas' requires probe of 'wds' devices to be successful;
so don't fail them.

Signed-off-by: Nathan Hintz <nlhintz@hotmail.com>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38763 3c298f89-4303-0410-b956-a3cf2f4a3e73