samples: modules: lvgl: demos: Migrate to v9.2

This patch changes the usage of LVGL functions which are typedefed in the
api map to their new version to anticipate their deprecation.

Signed-off-by: Fabian Blatz <[email protected]>

Author: faxe1008

samples/modules/lvgl/demos/src/main.c

@@ -38,15 +38,15 @@ int main(void)
 	CONFIG_LV_USE_DEMO_STRESS, or CONFIG_LV_USE_DEMO_WIDGETS
 #endif
 
-	lv_task_handler();
+	lv_timer_handler();
 	display_blanking_off(display_dev);
 #ifdef CONFIG_LV_Z_MEM_POOL_SYS_HEAP
 	lvgl_print_heap_info(false);
 #else
 	printf("lvgl in malloc mode\n");
 #endif
 	while (1) {
-		uint32_t sleep_ms = lv_task_handler();
+		uint32_t sleep_ms = lv_timer_handler();
 
 		k_msleep(MIN(sleep_ms, INT32_MAX));
 	}