Revert "x86-64: Reverse order of bootmem lists"

As requested by Thomas Gleixner <tglx@linutronix.de>:

  "5d3d0f77

 breaks a couple of ARM
   boards, which depend on the historical bootmem allocation order.
   There is a cleaner solution around to remove the pgdat list
   completely, but this is a topic for post 2.6.14

   Andi signalled ACK already."

Signed-off-by: Linus Torvalds <torvalds@osdl.org>