ksm: Provide support to use deferred timers for scanner thread

KSM thread to scan pages is getting schedule on definite timeout.
That wakes up CPU from idle state and hence may affect the power
consumption. Provide an optional support to use deferred timer
which suites low-power use-cases.

To enable deferred timers,
$ echo 1 > /sys/kernel/mm/ksm/deferred_timer

Change-Id: I07fe199f97fe1f72f9a9e1b0b757a3ac533719e8
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
 Added support for delayed ack.

https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?h=kk_2.7-stable&id=73989a4b345bba0efca96cc86b0258e83884ff63
SmittyV
zram/zsmalloc issues in very low memory conditions.

---- Alucard24 authored
SmittyV