Fix WLR_DIRECTION enums.

Having 0 as an enum value causes wlr_output_layout_adjacent_output() to
never match WLR_DIRECTION_UP.

include/wlr/types/wlr_output_layout.h

@@ -105,9 +105,9 @@ struct wlr_output *wlr_output_layout_get_center_output(
 		struct wlr_output_layout *layout);
 
 enum wlr_direction {
-	WLR_DIRECTION_UP = 0,
+	WLR_DIRECTION_UP = 1,
-	WLR_DIRECTION_DOWN = 1,
+	WLR_DIRECTION_DOWN = 2,
-	WLR_DIRECTION_LEFT = 2,
+	WLR_DIRECTION_LEFT = 3,
 	WLR_DIRECTION_RIGHT = 4,
 };