thermal: Add driver for Armada 370/XP SoC thermal management

This driver supports both Armada 370 and Armada XP SoC
thermal management controllers.

Armada 370 has a register to check a valid temperature, whereas
Armada XP does not. Each has a different initialization (i.e. calibration)
function. The temperature conversion formula is the same for both.

The controller present in each SoC have a very similar feature set,
so it corresponds to have one driver to support both of them.

Although this driver may present similarities to Dove and Kirkwood
thermal driver, the exact differences and coincidences are not fully
known. For this reason, support is given through a separate driver.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>