Fix number clash: EVP_F_AESNI_XTS_INIT_KEY vs EVP_F_EVP_MD_BLOCK_SIZE

The three macros EVP_F_AESNI_XTS_INIT_KEY, EVP_F_AES_T4_XTS_INIT_KEY
and EVP_F_AES_XTS_INIT_KEY are affected.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8682)