wlcore: add mac override parameter

Note the cmdline parameter would be wlcore.mac=nn:nn:nn:nn:nn:nn

This moved since the 3.0.x kernels because of WL12xx restructuring.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>

Conflicts:
	drivers/net/wireless/wl12xx/main.c