ppc64: Enable HV and PR KVM
    
    Unlike other platforms, PPC64 supports 2 types of KVM:
    1. PR KVM emulated in user space - works on every PPC64 platform, even on
    old POWERMAC; does not require hypervisor-enabled host CPU (POWER5+ and
    newer); does not require OPAL;
    
    2. HV KVM - this requires hypervisor-enabled CPU and OPAL - i.e. recent
    POWER7/8 CPUs running as a "powernv" platform only.
    
    So PPC64 KVM is split into 3 kernel modules - kvm_pr, kvm_hv and kvm,
    the latter contains bits of code common for both types of KVM.
    
    Recent QEMU supports a "kvm-type" machine option and can instantiate
    the requested type of KVM.
    
    Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>