aubinator: Drop decode_structure() helper.
aubinator: Drop decode_structure() helper.

It made more sense when decode_group() took a bunch of extra options,
but now that there's only one...we may as well pass 0 and call it a day.

Reviewed-by: Lionel Landwerlin <9463032a5b99ffad10f36631678a833369a311b5@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler