glsl: make use of glsl_type::is_array()

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>

src/compiler/glsl/link_varyings.cpp

@@ -1678,7 +1678,7 @@ varying_matches::compute_packing_order(const ir_variable *var)
 {
    const glsl_type *element_type = var->type;
 
-   while (element_type->base_type == GLSL_TYPE_ARRAY) {
+   while (element_type->is_array()) {
       element_type = element_type->fields.array;
    }