[PATCH] x86_64: e820.c needs pgtable.h

arch/x86_64/kernel/e820.c:42: error: 'MAXMEM' undeclared here (not in a function)

Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>