There are some heuristics in the PPC power management code that try to find
out if the particular hardware we're running on supports proper power management
or just hangs the machine when going into nap mode.

Since we know that KVM is safe with nap, let's force enable it in the PV code
once we're certain that we are on a KVM VM.
Signed-off-by: Alexander Graf <agraf@suse.de>