RFR: 8339300: CollectorPolicy.young_scaled_initial_ergo_vm gtest fails on ppc64 based platforms

[Matthias Baesken]

We currently fail in CollectorPolicy.young_scaled_initial_ergo_vm after [JDK-8258483](https://bugs.openjdk.org/browse/JDK-8258483) came in.
AIX / Linux ppc64le show this error :

[ RUN ] CollectorPolicy.young_scaled_initial_ergo_vm
test/hotspot/gtest/gc/shared/test_collectorPolicy.cpp:122: Failure
Expected equality of these values:
  expected
    Which is: 44695552
  NewSize
    Which is: 41943040

test/hotspot/gtest/gc/shared/test_collectorPolicy.cpp:78: Failure
Expected: checker->execute() doesn't generate new fatal failures in the current thread.
  Actual: it does.

[ FAILED ] CollectorPolicy.young_scaled_initial_ergo_vm (0 ms)

So the decrease form 80M to 40M was too much for these platforms (they slightly differ in ergo/startup behavior).

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

Commit messages:
 - JDK-8339300

Changes: https://git.openjdk.org/jdk/pull/20820/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20820&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339300
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/20820.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20820/head:pull/20820

PR: https://git.openjdk.org/jdk/pull/20820