Originally from Venkatesh Pallipadi for i386

An e820 map with more than 18 entries would overflow into the EDID area in the
zero page.  Fix this.

This is a x86-64 port of Venka's i386 version.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>