spirv: Add support for using derefs for UBO/SSBO access

For now, it's hidden behind a cap.  Hopefully, we can eventually drop
that along with all the manual offset code in spirv_to_nir.

Reviewed-by: Alejandro PiƱeiro <apinheiro@igalia.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Tested-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
9 files changed