Add support for the MediaTek latest generation IEEE 802.11ax 4x4
device MT7915E, which supports concurrent dual-band operation at
both 5GHz and 2.4GHz.

Note that this patch just add basic part and will add more HE
capabilities support in the further patches.

The driver supports AP, Station, Mesh and monitor mode.
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Signed-off-by: NShayne Chen <shayne.chen@mediatek.com>
Signed-off-by: NChih-Min Chen <chih-min.chen@mediatek.com>
Suggested-by: NShihwei Lin <shihwei.lin@mediatek.com>
Tested-by: NEvelyn Tsai <evelyn.tsai@mediatek.com>
Acked-by: NYiwei Chung <yiwei.chung@mediatek.com>
Acked-by: NYF Luo <yf.luo@mediatek.com>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>