Look for gaps in the e820 memory map to put PCI resources in.

This hopefully fixes problems with the PCI code assigning 32bit BARs MMIO
resources which are >32bit.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>