Extend mt76_connac_mcu_uni_add_dev with per-link BSS configuration.

The patch we created is a prerequisite to enable the MLO function in the
driver. It is purely a refactoring patch so the functionality should
remain unchanged.

We also extend link_idx field in mt76_connac_bss_basic_tlv for the firmware
to able to identify the link index in the MLO mode that is not harmful
for the current non-MLO mode.
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/20240613030241.5771-6-sean.wang@kernel.orgSigned-off-by: Felix Fietkau <nbd@nbd.name>