mac80211: add max channel calculation utility function

The utility function has no uses yet. It is aimed
at future chanctx reservation management and
channel switching.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 3dd2111..bfc3ca5 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1822,6 +1822,7 @@
 				 const struct cfg80211_chan_def *chandef,
 				 enum ieee80211_chanctx_mode chanmode,
 				 u8 radar_detect);
+int ieee80211_max_num_channels(struct ieee80211_local *local);
 
 #ifdef CONFIG_MAC80211_NOINLINE
 #define debug_noinline noinline