thermal/drivers/cpuidle_cooling: Change the registration function

Today, there is no user for the cpuidle cooling device. The targetted
platform is ARM and ARM64.

The cpuidle and the cpufreq cooling device are based on the device tree.

As the cpuidle cooling device can have its own configuration depending
on the platform and the available idle states. The DT node description
will give the optional properties to set the cooling device up.

Do no longer rely on the CPU node which is prone to error and will
lead to a confusion in the DT because the cpufreq cooling device is
also using it. Let initialize the cpuidle cooling device with the DT
binding.

This was tested on:
 - hikey960
 - hikey6220
 - rock960
 - db845c

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200429103644.5492-3-daniel.lezcano@linaro.org