drivers: dio: add missing iounmap() in dio_init()

If kzalloc() fails, iounmap() need be called in error path.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220511064506.3398512-1-yangyingliang@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>