thermal: devfreq_cooling: Use PM QoS to set frequency limits

Now that devfreq supports limiting the frequency range of a device
through PM QoS make use of it instead of disabling OPPs that should
not be used.

The switch from disabling OPPs to PM QoS introduces a subtle behavioral
change in case of conflicting requests (min > max): PM QoS gives
precedence to the MIN_FREQUENCY request, while higher OPPs disabled
with dev_pm_opp_disable() would override MIN_FREQUENCY.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200318114548.19916-4-lukasz.luba@arm.com