thermal: rockchip: better to compatible the driver for different SoCs

The current driver is default to register the two thermal sensors
in probe since some SoCs maybe only have one sensor for thermal.

In some cases, the channel 0 is not always the cpu or gpu sensor.
So add the channel can be configured for sensors.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>