radv: Use NIR barycentric intrinsics

We have to add a few lowering to deal with things that used to be dealt
with inline when creating inputs. We also move the code that fills out
the radv_shader_variant_info struct for linking purposes to
radv_shader.c, as it's no longer tied to the NIR->LLVM lowering.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/vulkan/radv_shader_info.c

@@ -224,7 +224,7 @@ gather_intrinsic_info(const nir_shader *nir, const nir_intrinsic_instr *instr,
 		      struct radv_shader_info *info)
 {
 	switch (instr->intrinsic) {
-	case nir_intrinsic_interp_deref_at_sample:
+	case nir_intrinsic_load_barycentric_at_sample:
 		info->ps.needs_sample_positions = true;
 		break;
 	case nir_intrinsic_load_draw_id: