sha/asm/sha512-armv8.pl: add NEON version of SHA256.
sha/asm/sha512-armv8.pl: add NEON version of SHA256.

This provides up to 30% better performance on some of recent processors.

Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl