aes/asm/aesni-sha*-x86_64.pl: fix IV handling in SHAEXT paths.

Initial IV was disregarded on SHAEXT-capable processors. Amazingly
enough bulk AES128-SHA* talk-to-yourself tests were passing.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2992)

(cherry picked from commit 08d09628)