soc: rockchip: mtd_vendor_storage: Register vendor_storage later

Since storage drivers register in module_init, So the vendor_storage
should be initiated after it.

Change-Id: Icefce56c54713dd56ef992ec527e65fce4f0c977
Signed-off-by: Jon Lin <jon.lin@rock-chips.com>

drivers/soc/rockchip/mtd_vendor_storage.c

@@ -447,4 +447,4 @@ static int __init vendor_storage_init(void)
 	return ret;
 }
 
-module_init(vendor_storage_init);
+device_initcall_sync(vendor_storage_init);