block/cfq: import from LK 3.2

http://lxr.free-electrons.com/source/?v=3.2
block/cfq: fix build error
block/cfq: check st->total_weight to prevent kernel panic caused by dividing by zero

Signed-off-by: Shilin Victor <chrono.monochrome@gmail.com>
mcde_hw: add sysfs interface to tweak various functions

example:
    echo mcde_handle_vcmp_tweak=off > /sys/kernel/mcde_hw/tweaks

Disable all tweaks only if noticed screen tearing:
    echo off > /sys/kernel/mcde_hw/tweaks

This commit based on commit 7804d8b274c32e04d65cf34a147d4c91e86fb72d
bln: fix derps