[PATCH] kdump: x86_64: add memmmap command line option

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From: Vivek Goyal <vgoyal@in.ibm.com>

- This patch introduces the memmap option for x86_64 similar to i386.

- memmap=exactmap enables setting of an exact E820 memory map, as specified
  by the user.

Changes in this version:

- Used e820_end_of_ram() to find the max_pfn as suggested by Andi kleen.

- removed PFN_UP & PFN_DOWN macros

- Printing the user defined map also.

Signed-off-by: Murali M Chakravarthy <muralim@in.ibm.com>
Signed-off-by: Hariprasad Nellitheertha <nharipra@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>