usb/net/asix_devices: Add USBNET HG20F9 ethernet dongle

usb/net/asix_devices: Add USBNET HG20F9 ethernet dongle

This USB ethernet adapter was purchased in anodyne packaging
from the computer store adjacent to linux.conf.au 2013 in
Canberra (Australia). A web search shows other recent
purchasers in Lancaster (UK) and Seattle (USA). Just like an
emergent virus, our age of e-commerce and airmail allows
underdocumented hardware to spread around the world instantly
using the vector of ridiculously low prices.

Paige Thompson, infected via eBay, discovered that the HG20F9
is a copy of the Asix 88772B; many viruses copy the RNA of
other viruses. See Paige's work at
<https://github.com/paigeadele/HG20F9>.
This patch uses her discovery to update the restructured Asix
driver in the current kernel.

Just as some viruses inhabit seemingly-healthy cells, the
HG20F9 uses the Vendor ID 0x066b assigned to Linksys Inc.
For the present there is no clash of Product ID 0x20f9.

Signed-off-by: Glen Turner <gdt@gdt.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>