revert commit cded932b,
"x86: fix pmd_bad and pud_bad to support huge pages", it causes
a bootup hang, as reported and bisected by Arjan van de Ven.
Bisected-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>