Revert "x86: create a non-zero sized bm_pte only when needed"

This reverts commit 698609bd

.

69860 breaks Xen booting, as it relies on head*.S to set up the fixmap
pagetables (as a side-effect of initializing the USB debug port).
Xen, however, does not boot via head*.S, and so the fixmap area is
not initialized.

The specific symptom of the crash is a fault in dmi_scan(), because
the pointer that early_ioremap returns is not actually present.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <49C43A8E.5090203@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>