wifi: mt76: connac: add eht support for phy mode config

Add eht configuration support in existing function
mt76_connac_get_phy_mode_v2() and export it for mt7925.

This is a preliminary patch to support mt7925 driver.

Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>