dt-bindings: thermal: Define BCM7216 thermal sensor compatible

BCM7216 is a 16nm process STB chip, which requires a different
compatible string to differentiate different temperature formulas.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200114190607.29339-4-f.fainelli@gmail.com

Documentation/devicetree/bindings/thermal/brcm,avs-tmon.txt

@@ -3,9 +3,13 @@
 Thermal management core, provided by the AVS TMON hardware block.
 
 Required properties:
-- compatible: must be "brcm,avs-tmon" and/or "brcm,avs-tmon-bcm7445"
+- compatible: must be one of:
+	"brcm,avs-tmon-bcm7216"
+	"brcm,avs-tmon-bcm7445"
+	"brcm,avs-tmon"
 - reg: address range for the AVS TMON registers
-- interrupts: temperature monitor interrupt, for high/low threshold triggers
+- interrupts: temperature monitor interrupt, for high/low threshold triggers,
+	      required except for "brcm,avs-tmon-bcm7216"
 - interrupt-names: should be "tmon"
 
 Example: