x86: fix vmemmap printout check

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: "Nick Piggin" <npiggin@suse.de>
Cc: "Mark McLoughlin" <markmc@redhat.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: "Eduardo Habkost" <ehabkost@redhat.com>
Cc: "Vegard Nossum" <vegard.nossum@gmail.com>
Cc: "Stephen Tweedie" <sct@redhat.com>
Cc: "Jeremy Fitzhardinge" <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>