thermal: imx_sc_thermal: Add hwmon support

Expose i.MX SC thermal sensors as HWMON devices.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1585192411-25593-1-git-send-email-Anson.Huang@nxp.com