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

src/compiler/nir/nir_intrinsics.py

@@ -364,6 +364,8 @@ intrinsic("vulkan_resource_index", src_comp=[1], dest_comp=1,
           flags=[CAN_ELIMINATE, CAN_REORDER])
 intrinsic("vulkan_resource_reindex", src_comp=[1, 1], dest_comp=1,
           indices=[DESC_TYPE], flags=[CAN_ELIMINATE, CAN_REORDER])
+intrinsic("load_vulkan_descriptor", src_comp=[1], dest_comp=0,
+          indices=[DESC_TYPE], flags=[CAN_ELIMINATE, CAN_REORDER])
 
 # variable atomic intrinsics
 #