Waypoints/Navigator: Use two different dataman storage places, keep old waypoints until all new ones are written

src/modules/dataman/dataman.c

@@ -111,7 +111,8 @@ static unsigned g_func_counts[dm_number_of_funcs];
 static const unsigned g_per_item_max_index[DM_KEY_NUM_KEYS] = {
 	DM_KEY_SAFE_POINTS_MAX,
 	DM_KEY_FENCE_POINTS_MAX,
-	DM_KEY_WAYPOINTS_OFFBOARD_MAX,
+	DM_KEY_WAYPOINTS_OFFBOARD_0_MAX,
+	DM_KEY_WAYPOINTS_OFFBOARD_1_MAX,
 	DM_KEY_WAYPOINTS_ONBOARD_MAX
 };