crypto: arm64/poly1305 - remove redundant shash algorithm

Since crypto/poly1305.c now registers a poly1305-$(ARCH) shash algorithm
that uses the architecture's Poly1305 library functions, individual
architectures no longer need to do the same.  Therefore, remove the
redundant shash algorithm from the arch-specific code and leave just the
library functions there.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>