cfg80211/mac80211: DFS setup chandef for cac event

To report channel width correctly we have
to send correct channel parameters from
mac80211 when calling cfg80211_cac_event().

This is required in case of using channel width
higher than 20MHz and we have to set correct
dfs channel state after CAC (NL80211_DFS_AVAILABLE).

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Reviewed-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
(cherry picked from http://mid.gmane.org/1382984824-3729-1-git-send-email-janusz.dziedzic@tieto.com)