[crac] RFR: Fix CPUFeatures crash on new->old CPU

[Jan Kratochvil]

- reproducible on i7-1165G7 "qemu-kvm -cpu host" for a checkpoint and "qemu-kvm -cpu SandyBridge" for its restore

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Commit messages:
 - Fix CPUFeatures crash on new->old CPU

Changes: https://git.openjdk.org/crac/pull/134/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=134&range=00
  Stats: 44 lines in 4 files changed: 33 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/crac/pull/134.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/134/head:pull/134

PR: https://git.openjdk.org/crac/pull/134