RFR: 8313141: Remove discarded volatile qualifier in assembler_aarch64.hpp

[Julian Waters]

ISO C++ asm is always implicitly volatile, as per https://gcc.gnu.org/onlinedocs/gcc/Basic-Asm.html, and all volatile qualifiers are always ignored if GNU asm was never used

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Commit messages:
 - 8313141

Changes: https://git.openjdk.org/jdk/pull/15031/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15031&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313141
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15031.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15031/head:pull/15031

PR: https://git.openjdk.org/jdk/pull/15031