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>

include/net/iw_handler.h

@@ -443,7 +443,7 @@ extern int dev_get_wireless_info(char * buffer, char **start, off_t offset,
 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... */

net/wireless/wext.c

@@ -1376,7 +1376,7 @@ static void rtmsg_iwinfo(struct net_device *dev, char *event, int event_len)
 void wireless_send_event(struct net_device *	dev,
 			 unsigned int		cmd,
 			 union iwreq_data *	wrqu,
-			 char *			extra)
+			 const char *		extra)
 {
 	const struct iw_ioctl_description *	descr = NULL;
 	int extra_len = 0;