wpa_supplicant: Use monotonic time for last_scan check

This just serves to check if there was a scan within
the last 5 seconds, hence it should use monotonic time.
While at it, also use os_reltime_expired().

Signed-hostap: Johannes Berg <johannes.berg@intel.com>

wpa_supplicant/bss.c

@@ -733,7 +733,7 @@ void wpa_bss_update_end(struct wpa_supplicant *wpa_s, struct scan_info *info,
 	struct wpa_bss *bss, *n;
 
 	wpa_s->last_scan_full = 0;
-	os_get_time(&wpa_s->last_scan);
+	os_get_reltime(&wpa_s->last_scan);
 	if (!new_scan)
 		return; /* do not expire entries without new scan */
 

wpa_supplicant/events.c

@@ -1428,13 +1428,13 @@ int wpa_supplicant_fast_associate(struct wpa_supplicant *wpa_s)
 #ifdef CONFIG_NO_SCAN_PROCESSING
 	return -1;
 #else /* CONFIG_NO_SCAN_PROCESSING */
-	struct os_time now;
+	struct os_reltime now;
 
 	if (wpa_s->last_scan_res_used <= 0)
 		return -1;
 
-	os_get_time(&now);
-	if (now.sec - wpa_s->last_scan.sec > 5) {
+	os_get_reltime(&now);
+	if (os_reltime_expired(&now, &wpa_s->last_scan, 5)) {
 		wpa_printf(MSG_DEBUG, "Fast associate: Old scan results");
 		return -1;
 	}

wpa_supplicant/wpa_supplicant_i.h

@@ -409,7 +409,7 @@ struct wpa_supplicant {
 	unsigned int last_scan_res_used;
 	unsigned int last_scan_res_size;
 	int last_scan_full;
-	struct os_time last_scan;
+	struct os_reltime last_scan;
 
 	struct wpa_driver_ops *driver;
 	int interface_removed; /* whether the network interface has been