RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v30]

[Suchismith Roy]

> JBS Issue : [JDK-8216437](https://bugs.openjdk.org/browse/JDK-8216437)
> 
> Currently acceleration code for GHASH is missing for PPC64. 
> 
> The current implementation utlilises SIMD instructions on Power and uses Karatsuba multiplication for obtaining the final result.

Suchismith Roy has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 58 commits:

 - Merge branch 'openjdk:master' into ghash_processblocks
 - comments
 - comments
 -  comments
 - use vsplitsb
 - change pattern for Linux, fix for AIX
 - change pattern for Linux, fix for AIX
 - change branch and remove not needed variables
 - change branch and remove not needed variables
 - remove not needed variables
 - ... and 48 more: https://git.openjdk.org/jdk/compare/0537c692...9231e7be

-------------

Changes: https://git.openjdk.org/jdk/pull/20235/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20235&range=29
  Stats: 183 lines in 2 files changed: 181 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20235.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20235/head:pull/20235

PR: https://git.openjdk.org/jdk/pull/20235