[PATCH] PPC64 Kdump documentation update

Patch from Mohan Kumar M to add the ppc64 portions of the kdump
documentation.

http://thread.gmane.org/gmane.linux.kernel/481689/focus=3375

Cc: Mohan Kumar M <mohan@in.ibm.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>