crypto: chacha20poly1305 - Use lib/crypto poly1305

Since the poly1305 algorithm is fixed, there is no point in going
through the Crypto API for it.  Use the lib/crypto poly1305 interface
instead.

For compatiblity keep the poly1305 parameter in the algorithm name.

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