KVM: arm64: Pass mm_ops through the visitor context

As a prerequisite for getting visitors off of struct kvm_pgtable, pass
mm_ops through the visitor context.

No functional change intended.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Ben Gardon <bgardon@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221107215644.1895162-4-oliver.upton@linux.dev