power_supply: Register power supply for thermal cooling device

This patch registers the power supply as a cooling device if the power
supply has support for charge throttling.

Now with this change low level drivers need not register with thermal
framework as it is automatically done by power supply framework.

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>