nir: Stop assuming glsl_get_length() returns 0 for vectors

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22580>

src/compiler/nir/nir.c

@@ -318,7 +318,7 @@ nir_create_variable_with_location(nir_shader *shader, nir_variable_mode mode, in
    /* Only supporting non-array, or arrayed-io types, because otherwise we don't
     * know how much to increment num_inputs/outputs
     */
-   assert(glsl_get_length(type) <= 1);
+   assert(glsl_type_is_vector_or_scalar(type) || glsl_type_is_unsized_array(type));
 
    const char *name;
    switch (mode) {