wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices

The driver first supports Filogic 680 PCI device, which is a Wi-Fi 7
chipset supporting concurrent tri-band operation at 6 GHz, 5 GHz, and
2.4 GHz with 4x4 antennas on each band.

Currently, mt7996 only supports tri-band HE or older mode.
EHT mode and more variants of Filogic 680 support will be introduced
in further patches.

Reviewed-by: Ryder Lee <ryder.lee@mediatek.com>
Co-developed-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Co-developed-by: Bo Jiao <Bo.Jiao@mediatek.com>
Signed-off-by: Bo Jiao <Bo.Jiao@mediatek.com>
Co-developed-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Signed-off-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Co-developed-by: MeiChia Chiu <meichia.chiu@mediatek.com>
Signed-off-by: MeiChia Chiu <meichia.chiu@mediatek.com>
Co-developed-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Co-developed-by: Money Wang <Money.Wang@mediatek.com>
Signed-off-by: Money Wang <Money.Wang@mediatek.com>
Co-developed-by: Evelyn Tsai <evelyn.tsai@mediatek.com>
Signed-off-by: Evelyn Tsai <evelyn.tsai@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>