mt76: add driver for MT7603E and MT7628/7688

This driver is for a newer generation of 2x2 MediaTek 802.11n chipsets.
MT7603E is a PCIe chip.
MT7628 and MT7688 are MIPS SoC devices with built-in WLAN.
MT7688 is limited to 1x1

This driver fully supports AP, station, mesh, ad-hoc and monitor mode.

Signed-off-by: Felix Fietkau <nbd@nbd.name>