target/ppc/kvm: don't pass cpu to kvm_get_smmu_info()

In a future patch the machine code will need to retrieve the MMU
information from KVM during machine initialization before the CPUs
are created.

Actually, KVM_PPC_GET_SMMU_INFO is a VM class ioctl, and thus, we
don't need to have a CPU object around. We just need for KVM to
be initialized and use the kvm_state global. This patch just does
that.

Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>