[foreign-memaccess+abi] RFR: Add missing canonicalLayouts to PPC64 and s390 linkers

[Jorn Vernee]

Some changes I forgot to commit when doing the earlier merge [1]. These are needed to build

[1]: https://github.com/openjdk/panama-foreign/pull/882

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Commit messages:
 - add missing canonicalLayouts to PPC64 and s390 linkers

Changes: https://git.openjdk.org/panama-foreign/pull/883/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=883&range=00
  Stats: 24 lines in 2 files changed: 24 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/883.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign.git pull/883/head:pull/883

PR: https://git.openjdk.org/panama-foreign/pull/883