Separate Japan's DFS pattern from FCC to control PPB threshold.

Currently all the radar detectors use the same threshold rate at
50%, but it's not able to achieve if data traffic rate is higher
than 40% because WLAN baseband used by ath9k and ath10k often fails
detecting radar pulses, so that SW cannot get enough radar reports
to achieve the rate.

Since Japan's W53 band requires 50% data traffic during its DFS
test we need to apply different threshold rate than others on it.
Hence define its own pattern to give flexibility to threshold rate.
Signed-off-by: Peter Oh <poh@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>