Extend AMO tester to use more than one thread

[abouteiller]

Motivation

Some of our testers are too simple/easy to pass. During GDA development we designed a harder AMO tester. This has been spun out of gda2develop because this breaks RO.

Technical Details

It is not clear ATM if the tester is malfunctioning or if there is a legit error in RO that is found by this test.

Test Plan

Run the modified functional test on RO, IPC, GDA

Test Result

• [x] test pass on IPC
• [ ] test pass on RO
• [x] test pass on GDA

Submission Checklist

• [x] Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.