KVM: PPC: Export MMU variables

Our shadow MMU code needs to know where the HTAB is located and how
big it is. So we need some variables from the kernel exported to
module space if KVM is built as a module.

CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Avi Kivity <avi@redhat.com>