KVM: ppc: Move to new TLB invalidate interface

Commit 2a4aca11 removed old method _tlbia().

Signed-off-by: Liu Yu <yu.liu@freescale.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>