dm crypt: fix missing error code return from crypt_ctr error path

Fix to return a negative error code from crypt_ctr()'s optional
parameter processing error path.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
(cherry picked from commit 44c144f9c8e8fbd73ede2848da8253b3aae42ec2)
Signed-off-by: Alex Shi <alex.shi@linaro.org>