dt-bindings: thermal: Add binding document for Mediatek thermal controller

This adds the device tree binding documentation for the mediatek thermal
controller found on Mediatek MT2701.

Signed-off-by: Dawei Chien <dawei.chien@mediatek.com>
Reviewed-by: Keerthy <j-keerthy@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

Documentation/devicetree/bindings/thermal/mediatek-thermal.txt

@@ -8,7 +8,9 @@ apmixedsys register space via AHB bus accesses, so a phandle to the APMIXEDSYS
 is also needed.
 
 Required properties:
-- compatible: "mediatek,mt8173-thermal"
+- compatible:
+  - "mediatek,mt8173-thermal" : For MT8173 family of SoCs
+  - "mediatek,mt2701-thermal" : For MT2701 family of SoCs
 - reg: Address range of the thermal controller
 - interrupts: IRQ for the thermal controller
 - clocks, clock-names: Clocks needed for the thermal controller. required