x86: Fix broken VMI in 2.6.27-rc..

The lowmem mapping table created by VMI need not depend on max_low_pfn
at all.  Instead we now create an extra large mapping which covers all
possible lowmem instead of the physical ram that is actually available.

This allows the vmi initialization to be done before max_low_pfn could
be computed. We also move the vmi_init code very early in the boot process
so that nobody accidentally breaks the fixmap dependancy.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Acked-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>