RFR: 8308143: [ppc] remove constant and add wrap-up for successor [v2]

[Amit Kumar]

> This is cosmetic change, which adds simple range check logic and changes -1 to NOREG_ENCODING. I liked the changes for s390x so aligning PPC with the same.

Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:

  fix incorrect brackets

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13997/files
  - new: https://git.openjdk.org/jdk/pull/13997/files/582d8a24..0c8c36fd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13997&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13997&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13997.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13997/head:pull/13997

PR: https://git.openjdk.org/jdk/pull/13997