wifi: mt76: mt7925: add link handling to txwi

add link handling to mt792x_tx and writing txwi.

Co-developed-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Co-developed-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/c0a7c0b33ea2640bcb4f13a5f79a8976b73fa8f2.1720248331.git.sean.wang@kernel.org


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