Add hardware accelerated version of POLYVAL for ARM64 CPUs with
Crypto Extensions support.

This implementation is accelerated using PMULL instructions to perform
the finite field computations.  For added efficiency, 8 blocks of the
message are processed simultaneously by precomputing the first 8
powers of the key.

Karatsuba multiplication is used instead of Schoolbook multiplication
because it was found to be slightly faster on ARM64 CPUs.  Montgomery
reduction must be used instead of Barrett reduction due to the
difference in modulus between POLYVAL's field and other finite fields.

More information on POLYVAL can be found in the HCTR2 paper:
"Length-preserving encryption with HCTR2":
https://eprint.iacr.org/2021/1441.pdfSigned-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>