crypto: testmgr - Add a longer ChaCha20 test vector

The AVX2 variant of ChaCha20 is used only for messages with >= 512 bytes
length. With the existing test vectors, the implementation could not be
tested. Due that lack of such a long official test vector, this one is
self-generated using chacha20-generic.

Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>