KVM: PPC: E500: Support hugetlbfs

With hugetlbfs support emerging on e500, we should also support KVM
backing its guest memory by it.

This patch adds support for hugetlbfs into the e500 shadow mmu code.

Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Avi Kivity <avi@redhat.com>