RFR: 8340439: AArch64: Extra entry declaration for assember test

[SendaoYan]

Hi all,
The function declaration `extern "C" void entry(CodeBuffer*);` in `src/hotspot/cpu/aarch64/templateInterpreterGenerator_aarch64.cpp` line 74, seems to used for AArch64 assember test.
The AArch64 assember test has been moved to `test/hotspot/gtest` by [JDK-8252684](https://bugs.openjdk.org/browse/JDK-8252684) , so I think this function declaration can be remove.

Additional testing:

- [ ] linux aarch64 jtreg(tier1/2/3 etc.) with release build
- [ ] linux aarch64 jtreg(tier1/2/3 etc.) with fastdebug build

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Commit messages:
 - 8340439: Extra entry declaration for assember test

Changes: https://git.openjdk.org/jdk/pull/21086/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21086&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340439
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21086.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21086/head:pull/21086

PR: https://git.openjdk.org/jdk/pull/21086