wifi: mt76: mt7925: add mt7925_[assign,unassign]_vif_chanctx

add mt7925_[assign,unassign]_vif_chanctx to assign and unassign
chanctx to the specific link configuration. If the chctx is not
pass in the parameter, we will look up the channel information
from link_conf->chanreq.oper.

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/15261879a16cb12674d6dea7703410baa6883799.1720248331.git.sean.wang@kernel.org


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