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