[jdk21u-dev] RFR: 8358310: ZGC: riscv, ppc ZPlatformAddressOffsetBits may return a too large value

[Martin Doerr]

Backport of [JDK-8358310](https://bugs.openjdk.org/browse/JDK-8358310). Applies cleanly, but JDK21 still contains the non-generational version of ZGC which should also get updated. I'm using the same values as in the generational version.

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Commit messages:
 - Backport 4618374269e8636c772d921ad0c2c2d9e5e3e643

Changes: https://git.openjdk.org/jdk21u-dev/pull/1845/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1845&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358310
  Stats: 21 lines in 4 files changed: 6 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1845.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1845/head:pull/1845

PR: https://git.openjdk.org/jdk21u-dev/pull/1845