postcopy: Load huge pages in one go

The existing postcopy RAM load loop already ensures that it
glues together whole host-pages from the target page size chunks sent
over the wire.  Modify the definition of host page that it uses
to be the RAM block page size and thus be huge pages where appropriate.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170224182844.32452-10-dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
