Uniformize comments for enum types in the XML file

Some of the comments in the XML file don't allow a proper attribution to the underlying type. For instance:

```xml













```

It would be more consistent with the rest of the XML file have this:
```xml













```
I would like to see this adopted as a general guideline as it allows gathering more semantic when using the XML file for code generation purposes.

Start by locating the XML source and reviewing existing require comments for enum groups, using the cl_khr_egl_image examples in the issue as the comparison point. Update the comments so they identify the underlying enum type or error-code group consistently, and consider the work done when the XML follows that guideline throughout.

Written by the indexing model from the issue text.