RFR: 8354650: [PPC64] Try to reduce register definitions [v2]

[David Briemann]

> Defines the 32 vector registers and removes the 64 vector scalar register definitions.

David Briemann has updated the pull request incrementally with one additional commit since the last revision:

  trigger tests

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25828/files
  - new: https://git.openjdk.org/jdk/pull/25828/files/0762e1ea..a75f0289

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25828&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25828&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25828.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25828/head:pull/25828

PR: https://git.openjdk.org/jdk/pull/25828