RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v18]

[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 40 commits:

 - Merge branch 'openjdk:master' into ghash_processblocks
 - restore chnges
 - restore chnges
 - permute vHigh,vLow
 - indentation
 - comments
 - vsx logic change
 - spaces
 - spaces
 - update references
 - ... and 30 more: https://git.openjdk.org/jdk/compare/40603a5b...6388d4e1

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

Changes: https://git.openjdk.org/jdk/pull/20235/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20235&range=17
  Stats: 167 lines in 2 files changed: 163 ins; 0 del; 4 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