ppc: remove cannot_destroy_with_object_finalize_yet

This removes the assert(kvm_enabled()) from kvmppc_host_cpu_initfn()

This assert can never be triggered as the function is only registered
when KVM is available (see also 4c315c27
"qdev: Protect device-list-properties against broken devices").

So we can remove the cannot_destroy_with_object_finalize_yet from
kvmppc_host_cpu_class_init() without fear and beyond reproach.
(as it has already be done for i386 with 771a13e9 "i386: Unset
cannot_destroy_with_object_finalize_yet on "host" model" and
e4356010 "target-i386: Remove assert(kvm_enabled()) from
host_x86_cpu_initfn()")

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170414083717.13641-3-lvivier@redhat.com>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Markus Armbruster <armbru@redhat.com>