crypto: lrw - Check for incorrect cipher name

If the cipher name does not start with 'ecb(' we should bail out, as done
in the 'create()' function in 'crypto/xts.c'.

Fixes: 700cb3f5

 ("crypto: lrw - Convert to skcipher")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>