wext: constify extra argument to wireless_send_event

This is never changed by the function, so can be marked const.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/iw_handler.h b/include/net/iw_handler.h
index 51b9a37d..2b3fbbb 100644
--- a/include/net/iw_handler.h
+++ b/include/net/iw_handler.h
@@ -443,7 +443,7 @@
 extern void wireless_send_event(struct net_device *	dev,
 				unsigned int		cmd,
 				union iwreq_data *	wrqu,
-				char *			extra);
+				const char *		extra);
 
 /* We may need a function to send a stream of events to user space.
  * More on that later... */