[10] RFR(L): 8185979: PPC64: Implement SHA2 intrinsic

[Gustavo Serra Scalet]

Hi,

Could you please review this specific PPC64 change to hotspot? By implementing this intrinsic I noticed a significant improvement when using SHA-2 (e.g: Sample run reduced 6.5s run to 2.8s for SHA256.)
 
JBS: https://bugs.openjdk.java.net/browse/JDK-8185979
Webrev: https://gut.github.io/openjdk/webrev/JDK-8185979/webrev/

Best regards,
Gustavo Serra Scalet