ksm: Add showmem notifier

KSM is yet another framework which may obfuscate some memory
problems. Use the showmem notifier to show how KSM is being
used to give some insight into potential issues or non-issues.

Change-Id: If82405dc33f212d085e6847f7c511fd4d0a32a10
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>