dm crypt: fix crypt_ctr_cipher_new return value on invalid AEAD cipher

If the user specifies invalid AEAD cipher, dm-crypt should return the
error returned from crypt_ctr_auth_spec, not -ENOMEM.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>