cfg80211: regulatory: allow getting DFS CAC time from userspace

Introduce DFS CAC time as a regd param, configured per REG_RULE and
set per channel in cfg80211. DFS CAC time is close connected with
regulatory database configuration. Instead of using hardcoded values,
get DFS CAC time form regulatory database. Pass DFS CAC time to user
mode (mainly for iw reg get, iw list, iw info). Allow setting DFS CAC
time via CRDA. Add support for internal regulatory database.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
[rewrap commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 8c9ba44..bfa9a0c 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -151,6 +151,7 @@
  * @dfs_state: current state of this channel. Only relevant if radar is required
  *	on this channel.
  * @dfs_state_entered: timestamp (jiffies) when the dfs state was entered.
+ * @dfs_cac_ms: DFS CAC time in milliseconds, this is valid for DFS channels.
  */
 struct ieee80211_channel {
 	enum ieee80211_band band;
@@ -165,6 +166,7 @@
 	int orig_mag, orig_mpwr;
 	enum nl80211_dfs_state dfs_state;
 	unsigned long dfs_state_entered;
+	unsigned int dfs_cac_ms;
 };
 
 /**