crypto: x86/polyval - Fix crashes when keys are not 16-byte aligned

crypto_tfm::__crt_ctx is not guaranteed to be 16-byte aligned on x86-64.
This causes crashes due to movaps instructions in clmul_polyval_update.

Add logic to align polyval_tfm_ctx to 16 bytes.

Cc: <stable@vger.kernel.org>
Fixes: 34f7f6c30112 ("crypto: x86/polyval - Add PCLMULQDQ accelerated implementation of POLYVAL")
Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto: x86/polyval - Add PCLMULQDQ accelerated implementation of POLYVAL

Add hardware accelerated version of POLYVAL for x86-64 CPUs with
PCLMULQDQ support.

This implementation is accelerated using PCLMULQDQ 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.

Schoolbook multiplication is used instead of Karatsuba multiplication
because it was found to be slightly faster on x86-64 machines.
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.pdf

Signed-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>