RFR: 8282477: [x86, aarch64] vmassert(_last_Java_pc == NULL, "already walkable"); fails with async profiler

[Johannes Bechberger]

Fix the assertion by replacing it by assertion that does not fail.

-------------

Commit messages:
 - Fix assertion in aarch64, x86 and riscv

Changes: https://git.openjdk.java.net/jdk/pull/8209/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8209&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282477
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8209.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8209/head:pull/8209

PR: https://git.openjdk.java.net/jdk/pull/8209