nir: add missing type to type_size_vec4()

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/glsl/nir/nir_lower_io.c

@@ -62,6 +62,8 @@ type_size_vec4(const struct glsl_type *type)
          size += type_size_vec4(glsl_get_struct_field(type, i));
       }
       return size;
+   case GLSL_TYPE_SUBROUTINE:
+      return 1;
    case GLSL_TYPE_SAMPLER:
       return 0;
    case GLSL_TYPE_ATOMIC_UINT: