tests/pkg_lvgl*: adapt to new behavior

tests/pkg_lvgl/main.c

@@ -121,10 +121,10 @@ int main(void)
     /* Enable backlight */
     disp_dev_backlight_on();
 
-    lvgl_start();
-
     /* Create the system monitor widget */
     sysmon_create();
 
+    lvgl_run();
+
     return 0;
 }

tests/pkg_lvgl_touch/main.c

@@ -57,7 +57,7 @@ int main(void)
     lv_obj_t * label = lv_label_create(btn, NULL);
     lv_label_set_text(label, "Click me");
 
-    lvgl_start();
+    lvgl_run();
 
     return 0;
 }