crypto: testmgr - add diff-splits of src/dst into default cipher config

This type of request is often happened in AF_ALG cases.
So add this vector in default cipher config array.

Signed-off-by: Zhang Yiqun <zhangyiqun@phytium.com.cn>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>