dm persistent data: packed struct should have an aligned() attribute too

stable inclusion
from linux-4.19.191
commit 77aab16c6185f15fedccf72094d6d9a59dadadba

--------------------------------

commit a88b2358 upstream.

Otherwise most non-x86 architectures (e.g. riscv, arm) will resort to
byte-by-byte access.

Cc: stable@vger.kernel.org
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>