FROMLIST: thermal: Make cooling device trip point writable from sysfs

Make it possible to change trip point for the cooling device instance
in the thermal zone. It would be helpful in case when cooling devices can
by bind to thermal zones using sysfs interface.

A proper trip point can be chosen for a cooling device by:
echo 2 > /sys/class/thermal/thermal_zoneX/cdev_Z_trip_point

It is also possible to unpin cooling device from trip point:
echo -1 > /sys/class/thermal/thermal_zoneX/cdev_Z_trip_point

Change-Id: I69e7a592b7d76cabafb422311b6dea74c19924ea
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191216140622.25467-3-lukasz.luba@arm.com


Bug: 132152924
Signed-off-by: TeYuan Wang <kamewang@google.com>
Bug: 155322354
(cherry picked from commit dba49f7921d207625ed979d9d0da3302195a0170)
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>