RFR: 8304716: Clean up G1Policy::calc_max_old_cset_length()

[Thomas Schatzl]

Hi all,

  please review this simplification of `G1Policy::calc_max_old_cset_length()`. It does not seem important to be clever here.

Depends on #13147.

Testing: gha

Thanks,
  Thomas

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

Depends on: https://git.openjdk.org/jdk/pull/13147

Commit messages:
 - just use ceil()
 - initial version

Changes: https://git.openjdk.org/jdk/pull/13148/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13148&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304716
  Stats: 10 lines in 1 file changed: 0 ins; 8 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13148.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13148/head:pull/13148

PR: https://git.openjdk.org/jdk/pull/13148