crypto: xts - Add ECB dependency

Since the
   commit f1c131b4
   crypto: xts - Convert to skcipher
the XTS mode is based on ECB, so the mode must select
ECB otherwise it can fail to initialize.

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>