wifi: mt76: mt7921: add Netgear AXE3000 (A8000) support

Issue: Though the Netgear AXE3000 (A8000) is based on the mt7921
chipset because of the unique USB VID:PID combination this device
does not initialize/register. Thus making it not plug and play.

Fix: Adds support for the Netgear AXE3000 (A8000) based on the Mediatek
mt7921au chipset. The method of action is adding the USD VID/PID
pair to the mt7921u_device_table[] array.

Notes: A retail sample of the Netgear AXE3000 (A8000) yeilds the following
from lsusb D 0846:9060 NetGear, Inc. Wireless_Device. This pair
0846:9060 VID:PID has been reported by other users on Github.

Signed-off-by: Reese Russell <git@qrsnap.io>
Signed-off-by: Felix Fietkau <nbd@nbd.name>