rijndael-vaes-avx2: perform checksumming inline

* cipher/rijndael-vaes-avx2-amd64.S
(_gcry_vaes_avx2_ocb_checksum): Remove.
(_gcry_vaes_avx2_ocb_crypt_amd64): Add inline checksumming.

VAES/AVX2/OCB encryption implementation had same issue with
performance drop with large buffers as did AES-NI/OCB implementation,
see e924ce456d5728a81c148de4a6eb23373cb70ca0 for details. Patch
changes VAES/AVX2/OCB to perform checksumming inline with encryption
and decryption instead of using 2-pass approach. Inline checksumming
also gives nice small ~6% speed boost too.

Benchmark on Intel Core i3-1115G4:

Before:
AES | nanosecs/byte mebibytes/sec cycles/byte auto Mhz

OCB enc |     0.044 ns/B     21569 MiB/s     0.181 c/B      4089
OCB dec |     0.045 ns/B     21298 MiB/s     0.183 c/B      4089

After:
AES | nanosecs/byte mebibytes/sec cycles/byte auto Mhz

OCB enc |     0.042 ns/B     22922 MiB/s     0.170 c/B      4089
OCB dec |     0.042 ns/B     22676 MiB/s     0.172 c/B      4089

• GnuPG-bug-id: T5875
• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>