Match PAL C64 cursor timing

src/c64_ui.c

@@ -54,7 +54,7 @@ static void cursor_blink(lv_timer_t *timer) {
   lv_obj_set_style_bg_opa(cursor,
                           cursor_visible ? LV_OPA_COVER : LV_OPA_TRANSP,
                           LV_PART_MAIN);
-  lv_timer_set_period(timer, cursor_visible ? 667 : 333);
+  lv_timer_set_period(timer, 400);
 }
 
 void c64_ui_create(void) {
@@ -77,5 +77,5 @@ void c64_ui_create(void) {
   lv_obj_set_style_bg_color(cursor, C64_LIGHT_BLUE, LV_PART_MAIN);
   lv_obj_set_style_bg_opa(cursor, LV_OPA_COVER, LV_PART_MAIN);
 
-  lv_timer_create(cursor_blink, 667, cursor);
+  lv_timer_create(cursor_blink, 400, cursor);
 }