crypto: x86/aes-gcm-vaes-avx2 - initialize full %rax return register

crypto: x86/aes-gcm-vaes-avx2 - initialize full %rax return register

Update aes_gcm_dec_final_vaes_avx2() to be consistent with
aes_gcm_dec_final_aesni() and aes_gcm_dec_final_vaes_avx512() by
initializing the full %rax return register instead of just %al.
Technically this is unnecessary, since these functions return bool.  But
I think it's worth being extra careful with the result of the tag
comparison and also keeping the different implementations consistent.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20251102015256.171536-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>