wifi: mt76: connac: Extend mt76_connac_mcu_uni_add_dev for MLO

wifi: mt76: connac: Extend mt76_connac_mcu_uni_add_dev for MLO

This commit extends the `mt76_connac_mcu_uni_add_dev` function to include
support for Multi-Link Operation (MLO). Additionally, backward
compatibility for MT7921 is preserved, enabling seamless integration with
existing setups.

Fixes: 86c051f2c418 ("wifi: mt76: mt7925: enabling MLO when the firmware supports it")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/20241211011926.5002-1-sean.wang@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>