cfg80211: rework chandef checking and export it

Some of the chandef checking that we do in cfg80211
to check if a channel is supported or not is also
needed in mac80211, so rework that a bit and export
the functions that are needed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -58,6 +58,8 @@
  * structures here describe these capabilities in detail.
  */
 
+struct wiphy;
+
 /*
  * wireless hardware capability structures
  */
@@ -387,6 +389,22 @@ const struct cfg80211_chan_def *
 cfg80211_chandef_compatible(const struct cfg80211_chan_def *chandef1,
 			    const struct cfg80211_chan_def *chandef2);
 
+/**
+ * cfg80211_chandef_valid - check if a channel definition is valid
+ * @chandef: the channel definition to check
+ */
+bool cfg80211_chandef_valid(const struct cfg80211_chan_def *chandef);
+
+/**
+ * cfg80211_chandef_usable - check if secondary channels can be used
+ * @wiphy: the wiphy to validate against
+ * @chandef: the channel definition to check
+ * @prohibited_flags: the regulatory chanenl flags that must not be set
+ */
+bool cfg80211_chandef_usable(struct wiphy *wiphy,
+			     const struct cfg80211_chan_def *chandef,
+			     u32 prohibited_flags);
+
 /**
  * enum survey_info_flags - survey information flags
  *
@@ -1045,9 +1063,6 @@ struct ieee80211_txq_params {
 	u8 aifs;
 };
 
-/* from net/wireless.h */
-struct wiphy;
-
 /**
  * DOC: Scanning and BSS list handling
  *