PPC: KVM: Fix g3beige and mac99 when HV is loaded

PPC: KVM: Fix g3beige and mac99 when HV is loaded

On PPC we have 2 different styles of KVM: PR and HV. HV can only virtualize
sPAPR guests while PR can virtualize everything that's reasonably close to
the host hardware platform.

As long as only one kernel module (PR or HV) is loaded, the "default" kvm type
is the module that's loaded. So if your hardware only supports PR mode you can
easily spawn a Mac VM.

However, if both HV and PR are loaded we default to HV mode. And in that case
the Mac machines have to explicitly ask for PR mode to get a working VM.

Fix this up by explicitly having the Mac machines ask for PR style KVM. This
fixes bootup of Mac VMs on systems where bot HV and PR kvm modules are loaded
for me.

Signed-off-by: Alexander Graf <agraf@suse.de>