spirv: add interface for drivers to define support extensions.

I expect over time the struct contents will change as all
drivers support stuff etc, but for now this should be a good
starting point.

Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>
5 files changed