target/ppc: Add kvmppc_hpt_needs_host_contiguous_pages() helper

target/ppc: Add kvmppc_hpt_needs_host_contiguous_pages() helper

KVM HV has a restriction that for HPT mode guests, guest pages must be hpa
contiguous as well as gpa contiguous.  We have to account for that in
various places.  We determine whether we're subject to this restriction
from the SMMU information exposed by KVM.

Planned cleanups to the way we handle this will require knowing whether
this restriction is in play in wider parts of the code.  So, expose a
helper function which returns it.

This does mean some redundant calls to kvm_get_smmu_info(), but they'll go
away again with future cleanups.

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