Fix base_generator vendorTags logic

The logic didn't correctly iterate through the children of tags,
causing the vendorTags list to be generated incorrectly.

scripts/generators/base_generator.py

@@ -125,8 +125,9 @@ def beginFile(self, genOpts):
         for platform in self.registry.tree.findall('platforms/platform'):
             self.vk.platforms[platform.get('name')] = platform.get('protect')
 
-        for tag in self.registry.tree.findall('tags'):
-            self.vk.vendorTags.append(tag.get('name'))
+        for tags in self.registry.tree.findall('tags'):
+            for tag in tags.findall('tag'):
+                self.vk.vendorTags.append(tag.get('name'))
 
         # No way known to get this from the XML
         self.vk.queueBits[Queues.TRANSFER]       = 'VK_QUEUE_TRANSFER_BIT'