ath: enhance radar detection by looking up chirp

Certain radar types such as FCC radar type 5 are using chirp
in their pulses, hence looking up the chirp status will enhance
to avoid false radar detection.

Signed-off-by: Peter Oh <poh@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>