[PATCH] x86_64: Allow kernel page tables upto the end of memory

Previously they would be only allocated before the kernel text at
1MB.  This limited the maximum supported memory to 128GB.
Now allow the e820 allocator to put them everywhere. Try
to put them beyond any DMA zones to avoid filling them up.
This should free some GFP_DMA memory compared to earlier kernels.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>