usb/asix: add Buffalo LUA-U2-GT 10/100/1000

The USB net adapter Buffalo LUA-U2-GT (0411:006e) carries a AX88178 chip.
Tested on the above HW.

Signed-off-by: Mattia Dongili <malattia@linux.it>
Acked-off-by: David Hollis <dhollis@davehollis.com>
Cc: Greg KH <greg@kroah.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>