gfxml2dto: Fix QA Issue: 'version-going-backwards' using gitpkgv from meta-oe

This gitpkgv class creates a sortable version string from the git revisions, by counting the revisions similar to git describe. So the next commit to the package will not generate this warning again.

I put it here as a test, but if this works fine, we might consider to change all our recipes in a similar way.