dm integrity: fix a crash if "recalculate" used without "internal_hash"

stable inclusion
from linux-4.19.171
commit cf750e09d17f25cf763644168417fcad73e3ce0c

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

commit 2d06dfec upstream.

Recalculate can only be specified with internal_hash.

Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Mikulas Patocka <mpatocka@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>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>