KVM: PPC: fix information leak to userland

Structure kvm_ppc_pvinfo is copied to userland with flags and
pad fields unitialized.  It leads to leaking of contents of
kernel stack memory.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>