RFR: 8312979: Fix assembler_aarch64.hpp after JDK-8311847

[Coleen Phillimore]

This passes linux-aarch64-debug.  Waiting for GHA to see if it passes windows-aarch64.

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Commit messages:
 - Maybe this is better.
 - 8312979: Fix assembler_aarch64.hpp after JDK-8311847

Changes: https://git.openjdk.org/jdk/pull/15023/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15023&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312979
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15023.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15023/head:pull/15023

PR: https://git.openjdk.org/jdk/pull/15023