test/zdtm: Adding ppc64 support

Adding ppc64le specific parts to run test on this architecture.

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Acked-by: Andrew Vagin <avagin@odin.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>