RFR: 8291798: VMRegImpl::print_on is broken after JDK-8289060

[Tobias Hartmann]

The fix for [JDK-8289060](https://bugs.openjdk.org/browse/JDK-8289060) broke printing of  the stack offset because `VMRegImpl::print_on` was not adjusted accordingly:

0x00007fa97503a12f: callq 0x00007fa97c6615a0 ; ImmutableOopMap {[825414996]=Oop }


The fix is to simply use the `reg2stack` method.

Thanks,
Tobias

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Commit messages:
 - Removed accidentally added test
 - 8291798: VMRegImpl::print_on is broken after JDK-8289060

Changes: https://git.openjdk.org/jdk/pull/9723/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9723&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291798
  Stats: 8 lines in 2 files changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/9723.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9723/head:pull/9723

PR: https://git.openjdk.org/jdk/pull/9723