mt76: connac: update sched_scan cmd usage

Update sched_scan command usage according to the current firmware
submitted into linux-firmware.git.

Fixes: 80fc1e37

 ("mt76: mt7921: rely on mt76_connac_mcu module for sched_scan and hw_scan")
Co-developed-by: Soul Huang <Soul.Huang@mediatek.com>
Signed-off-by: Soul Huang <Soul.Huang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>