dm crypt: fix error return code in crypt_ctr()

commit 3cc2e57c4beabcbbaa46e1ac6d77ca8276a4a42d upstream.

Fix to return error code -ENOMEM from the mempool_create_kmalloc_pool()
error handling case instead of 0, as done elsewhere in this function.

Fixes: ef43aa38 ("dm crypt: add cryptographic data integrity protection (authenticated encryption)")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>