aes-amd64-vaes: fix fast exit path in XTS function
* cipher/rijndael-vaes-avx2-amd64.S (_gcry_vaes_avx2_xts_crypt_amd64): On fast exit path, compare number of blocks left against '1' instead of '0' as following branch is 'less than'.
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>