Add test vectors for Speck128-XTS, generated in userspace using C code.
The inputs were borrowed from the AES-XTS test vectors.

Both xts(speck128-generic) and xts-speck128-neon pass these tests.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>