ath9k: feed only active spectral / dfs-detector

Radar pulse and spectral scan reports are provided by the HW
with the ATH9K_RXERR_PHY flag set. Those are forwarded to
the dfs-detector and spectral module for further processing.

For some older chips, the pre-conditions checked in those
modules are ambiguous, since ATH9K_PHYERR_RADAR is used to
tag both types. As a result, spectral frames are fed into
the dfs-detector and vice versa.

This could lead to a false radar detection on a non-DFS
channel (which is uncritical), but more relevant it causes
useless CPU load for processing invalid frames.

This commit ensures that the dfs-detector and spectral
collector are only fed when they are active.

Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>