wifi: mt76: fix 6GHz high channel not be scanned

mt76 scan command only support 64 channels currently. If the
channel count is larger than 64(for 2+5+6GHz), some channels will
not be scanned. Hence change the scan type to full channel scan
in case of the command cannot include proper list for chip.

Fixes: 399090ef ("mt76: mt76_connac: move hw_scan and sched_scan routine in mt76_connac_mcu module")
Reported-by: Ben Greear <greearb@candelatech.com>
Tested-by: Isaac Konikoff <konikofi@candelatech.com>
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>