wireless: correct sparse warning in wext-compat.c

  CHECK   net/wireless/wext-compat.c
net/wireless/wext-compat.c:1434:5: warning: symbol 'cfg80211_wext_siwpmksa' was not declared. Should it be static?

Add declaration in cfg80211.h.  Also add an EXPORT_SYMBOL_GPL, since all
the peer functions have it.
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

include/net/cfg80211.h

@@ -1963,6 +1963,10 @@ int cfg80211_wext_giwap(struct net_device *dev,
 			struct iw_request_info *info,
 			struct sockaddr *ap_addr, char *extra);
 
+int cfg80211_wext_siwpmksa(struct net_device *dev,
+			   struct iw_request_info *info,
+			   struct iw_point *data, char *extra);
+
 /*
  * callbacks for asynchronous cfg80211 methods, notification
  * functions and BSS handling helpers

net/wireless/wext-compat.c

@@ -1471,6 +1471,7 @@ int cfg80211_wext_siwpmksa(struct net_device *dev,
 		return -EOPNOTSUPP;
 	}
 }
+EXPORT_SYMBOL_GPL(cfg80211_wext_siwpmksa);
 
 static const iw_handler cfg80211_handlers[] = {
 	[IW_IOCTL_IDX(SIOCGIWNAME)]	= (iw_handler) cfg80211_wext_giwname,