Rename qcrypto_block_*crypt_helper to qcrypto_block_cipher_*crypt_helper,
as it's not about QCryptoBlock. This is needed to introduce
qcrypto_block_*crypt_helper in the next commit, which will have
QCryptoBlock pointer and than will be able to use additional fields of
it, which in turn will be used to implement thread-safe QCryptoBlock
operations.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>