power: smb5: Add support for thermal throttling

Expose power_supply property to allow userspace throttling
algorithm to configure ICL.

Change-Id: I70233fadda4dbbd878db7cc641730437ea9f28c6
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>