RFR: 8326235: RISC-V: Size CodeCache for short calls encoding

[Robbin Ehn]

Hi, please consider.

This limits the code cache to a size such that all code cache -> code cache calls and jump may always use auipc+jalr.
(this is what we do in practice)
Thus we can fix the encoding for those and not have variable encoding.
The reduction of the size is just 2k, but due to option passing the real reduction is probably 1M.
-XX:ReservedCodeCacheSize=2047M (down from 2048)

Note, specifying '2G' gives the message:

> Invalid ReservedCodeCacheSize=2048M. Must be at most 2047M.

Manually test, no test I found uses this large code cache.

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Commit messages:
 - Change RV code cache size.

Changes: https://git.openjdk.org/jdk/pull/17924/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17924&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326235
  Stats: 10 lines in 2 files changed: 8 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17924.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17924/head:pull/17924

PR: https://git.openjdk.org/jdk/pull/17924