powercap/drivers/dtpm: Add dtpm devfreq with energy model support

Currently the dtpm supports the CPUs via cpufreq and the energy
model. This change provides the same for the device which supports
devfreq.

Each device supporting devfreq and having an energy model can be added
to the hierarchy.

The concept is the same as the cpufreq DTPM support: the QoS is used
to aggregate the requests and the energy model gives the value of the
instantaneous power consumption ponderated by the load of the device.

Cc: Chanwoo Choi <cwchoi00@gmail.com>
Cc: Lukasz Luba <lukasz.luba@arm.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20220128163537.212248-5-daniel.lezcano@linaro.org