Revert "Work around RHBZ #1769600 on ppc64"

This reverts commit 8f53b9f5f8.

similar revert already done since a while in os-autoinst-distri-fedora
"e020b87  Drop the pseries-4.0 workaround for ppc64le"

createhdds.py

@@ -311,10 +311,6 @@ class VirtInstallImage(object):
             # openQA server:
             # https://bugzilla.redhat.com/show_bug.cgi?id=1387798
             args.extend(("--network", "user"))
-            # Workaround a qemu/ppc64 bug in F31:
-            # https://bugzilla.redhat.com/show_bug.cgi?id=1769600
-            if arch in ['ppc64','ppc64le']:
-                args.extend(("--machine", "pseries-4.0"))
             # run the command, timing out after 1 hour; sometimes creation
             # seems to just get mysteriously stuck, we need to bail and
             # retry in this case