spirv: Allow block-decorated struct types for constants

Whenever a struct type is decorated Block or BufferBlock we turn that
into a GLSL_TYPE_INTERFACE.  Since these decorations can end up random
places, we should allow them for constants.

Closes: #3252
Fixes: 9d0ae777dd "spirv: Use interface type for block and buffer..."
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5855>

src/compiler/nir/nir_print.c

@@ -399,6 +399,7 @@ print_constant(nir_constant *c, const struct glsl_type *type, print_state *state
       break;
 
    case GLSL_TYPE_STRUCT:
+   case GLSL_TYPE_INTERFACE:
       for (i = 0; i < c->num_elements; i++) {
          if (i > 0) fprintf(fp, ", ");
          fprintf(fp, "{ ");

src/compiler/spirv/spirv_to_nir.c

@@ -256,7 +256,8 @@ vtn_const_ssa_value(struct vtn_builder *b, nir_constant *constant,
       break;
    }
 
-   case GLSL_TYPE_STRUCT: {
+   case GLSL_TYPE_STRUCT:
+   case GLSL_TYPE_INTERFACE: {
       unsigned elems = glsl_get_length(val->type);
       val->elems = ralloc_array(b, struct vtn_ssa_value *, elems);
       for (unsigned i = 0; i < elems; i++) {