kvm: selftests: stop lying to aarch64 tests about PA-bits

Let's add the 40 PA-bit versions of the VM modes, that AArch64
should have been using, so we can extend the dirty log test without
breaking things.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>