dt-bindings: thermal: mediatek: make resets property optional

MT8516 Thermal IP does not support reset. Make the resets property
optional in order to be able to support MT8516 SoC.
Signed-off-by: Fabien Parent <fparent@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201021164231.3029956-1-fparent@baylibre.com

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

@@ -20,12 +20,12 @@ Required properties:
                        clocks are:
 		       "therm":	 Main clock needed for register access
 		       "auxadc": The AUXADC clock
-- resets: Reference to the reset controller controlling the thermal controller.
 - mediatek,auxadc: A phandle to the AUXADC which the thermal controller uses
 - mediatek,apmixedsys: A phandle to the APMIXEDSYS controller.
 - #thermal-sensor-cells : Should be 0. See Documentation/devicetree/bindings/thermal/thermal-sensor.yaml for a description.
 
 Optional properties:
+- resets: Reference to the reset controller controlling the thermal controller.
 - nvmem-cells: A phandle to the calibration data provided by a nvmem device. If
                unspecified default values shall be used.
 - nvmem-cell-names: Should be "calibration-data"