wifi: mt76: mt7925: update mt7925_mac_link_bss_add for MLO

Update band_idx in per-link BSS to be auto for the MLO-enabled firmware
and the MLO-enabled firmware only supports omac index in 0.

The change remains compatible with the non-MLO mode and the older firmware.

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/37fcf3ea7b4883840d61f97231277b297e1b15a3.1720248331.git.sean.wang@kernel.org


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