mesa: Drop enums that had been removed in later revs of specs.

mesa: Drop enums that had been removed in later revs of specs.

Mesa hasn't been using these enums and the finalized specs don't reference
them, so losing them from our generated enum-to-string code should be
fine.  Reduces diffs to generating from Khronos XML, which has these enums
noted defined but commented out from any consumers.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>