cfg80211: increase scan result expire time

Using background scanning in mac80211 the time a scan needs to
finish can exceed 10 seconds. Hence, increase the scan results
expire time to 15 seconds which should be sufficient.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/scan.c

@@ -15,7 +15,7 @@
 #include "core.h"
 #include "nl80211.h"
 
-#define IEEE80211_SCAN_RESULT_EXPIRE	(10 * HZ)
+#define IEEE80211_SCAN_RESULT_EXPIRE	(15 * HZ)
 
 void __cfg80211_scan_done(struct work_struct *wk)
 {