mac80211: constify IE parsing

Make all the parsed IE pointers const, and propagate
the change to all the users etc.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
index a9549fc..a2c2258 100644
--- a/net/mac80211/vht.c
+++ b/net/mac80211/vht.c
@@ -13,10 +13,11 @@
 #include "rate.h"
 
 
-void ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
-					 struct ieee80211_supported_band *sband,
-					 struct ieee80211_vht_cap *vht_cap_ie,
-					 struct sta_info *sta)
+void
+ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
+				    struct ieee80211_supported_band *sband,
+				    const struct ieee80211_vht_cap *vht_cap_ie,
+				    struct sta_info *sta)
 {
 	struct ieee80211_sta_vht_cap *vht_cap = &sta->sta.vht_cap;