Setup chandef for radar event correctly, before we
will clear this in ieee80211_dfs_cac_cancel() function.

Without this patch mac80211 will report wrong channel
width in case we will get radar event during active CAC.
Signed-off-by: NJanusz Dziedzic <janusz.dziedzic@tieto.com>
Reviewed-by: NLuis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>