net: asix: add support for the Billionton GUSB2AM-1G-B USB adapter

Just another AX88178-based 10/100/1000 USB-to-Ethernet dongle. This one
shows up in lsusb as: "ID 08dd:0114 Billionton Systems, Inc".

Signed-off-by: Chia-Sheng Chang <changchias@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Luca Ceresoli <luca@lucaceresoli.net>
Cc: Christoph Jaeger <cj@linux.com>
Cc: "Woojung.Huh@microchip.com" <Woojung.Huh@microchip.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Markus Elfring <elfring@users.sourceforge.net>
Cc: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Cc: netdev@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>