thermal: add stm32 thermal driver

Add support for DTS thermal sensor that can be
found on some STM32 platforms.

This driver is based on OF and works in interrupt
mode.

It offers two temperature trip points:
passive and critical. The first is intended for
passive cooling notification while the second is
used for over-temperature reset.

Signed-off-by: David Hernandez Sanchez <david.hernandezsanchez@st.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>