[Improvement] simplify inner tag name (#395)

packages/switch/index.vue

@@ -1,7 +1,7 @@
 <template>
   <div class="van-switch" :class="[`van-switch--${value ? 'on' : 'off'}`, { 'van-switch--disabled': disabled }]" @click="toggleState">
     <div class="van-switch__node van-hairline-surround">
-      <van-loading v-if="loading" class="van-switch__loading" />
+      <loading v-if="loading" class="van-switch__loading" />
     </div>
     <div class="van-switch__bg" />
   </div>
@@ -14,7 +14,7 @@ export default {
   name: 'van-switch',
 
   components: {
-    [Loading.name]: Loading
+    Loading
   },
 
   props: {