wlcore/wl18xx: add radar_debug_mode handling

Add debugfs key (under CFG80211_CERTIFICATION_ONUS
configuration) to set/clear radar_debug_mode.
In this mode, the driver simply ignores radar
events (but prints them).

The fw is notified about this mode through
a special generic_cfg_feature command.

This mode is relevant only for ap mode. look for
it when initializing ap vif.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>