Simplify default export

This removes unnecessary variable declarations where the default object is an object.

src/ol/layer/Property.js

@@ -1,10 +1,11 @@
 /**
  * @module ol/layer/Property
  */
+
 /**
  * @enum {string}
  */
-var _ol_layer_Property_ = {
+export default {
   OPACITY: 'opacity',
   VISIBLE: 'visible',
   EXTENT: 'extent',
@@ -13,5 +14,3 @@ var _ol_layer_Property_ = {
   MIN_RESOLUTION: 'minResolution',
   SOURCE: 'source'
 };
-
-export default _ol_layer_Property_;

src/ol/layer/TileProperty.js

@@ -1,12 +1,11 @@
 /**
  * @module ol/layer/TileProperty
  */
+
 /**
  * @enum {string}
  */
-var _ol_layer_TileProperty_ = {
+export default {
   PRELOAD: 'preload',
   USE_INTERIM_TILES_ON_ERROR: 'useInterimTilesOnError'
 };
-
-export default _ol_layer_TileProperty_;