[PATCH] x86_64: Don't try to put kernel page tables beyond ZONE_DMA32.

For not fully explained reasons it broke mem=... on several setups.

Also minor cleanup.

Cc: axboe@suse.de

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