bmips: dgnd3700v2: add b43 wireless driver
Apart from the embedded BCM6362 wireless, Netgear DGND3700v2 has external
BCM43228 wireless connected by PCIe.
Fallback SPROM isn't needed for this one because it has a physical SPROM.
Signed-off-by: Álvaro Fernández Rojas <[email protected]>