RFR: 8301067: RISC-V: better error message when reporting unsupported satp modes

[Feilong Jiang]

Add more detailed information to the error log when reporting unsupported stap modes.
Currently, RISC-V port only supports up to sv48.

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Commit messages:
 - add more information when reporting unsuppoted satp modes

Changes: https://git.openjdk.org/jdk/pull/12247/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12247&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301067
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12247.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12247/head:pull/12247

PR: https://git.openjdk.org/jdk/pull/12247