[PATCH] x86-64: Remove redundant max_mapnr and replace with end_pfn

The FLATMEM people added it, but there doesn't seem a good reason
because end_pfn is identical.

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