mt76: mt76x02: fix ED/CCA enabling/disabling

ED/CCA needs to be disable before stopping the MAC to avoid hangs from tx
being blocked. It must only be enabled again after the MAC has been started
again.
In many places this wasn't done properly, so fix this by always clearing
the relevant ED/CCA bits in mt76x2_mac_stop and set it up again after
channel change or calibration is done

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