PM: devfreq: Allow userspace configuration of simple_ondemand

/sys/class/devfreq/fdb00000.qcom,kgsl-3d0/simple_ondemand

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
PM: devfreq: Always reflect a change of polling interval

Change-Id: Ie895bdf1ed1126e05483890f7ed64ac05890710a