cfg80211: reg: set DFS CAC time in case of custom regd

Set DFS CAC time also in case of using custom
and strict regulatory from drivers. In other case
we could have unset DFS CAC time directly after
driver loaded and before issue regulatory set from
user mode.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>