thermal: Introduce Amazon's Annapurna Labs Thermal Driver

This is a generic thermal driver for simple MMIO sensors, of which
amazon,al-thermal is one.

This device uses a single MMIO transaction to read the temperature and
report it to the thermal subsystem.

Signed-off-by: Talel Shenhar <talel@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>