i965: Unhardcode a few more stage names and abbreviations.

i965: Unhardcode a few more stage names and abbreviations.

The stage_abbrev and stage_name fields in backend_visitor provide what
we need without any additional effort.  It also means we'll get the
right names for compute shaders, SIMD8 geometry shaders, and both kinds
of tessellation shaders.

This does unfortunately change the capitalization of the stage
abbreviation in the INTEL_DEBUG=optimizer output filenames.  It doesn't
seem worth adding code to handle, though.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>