Convert the 'generic-adc-thermal' binding to DT schema format.

The binding said '#thermal-sensor-cells' should be 1, but all in tree
users are 0 and 1 doesn't make sense for a single channel.

Drop the example's related providers and consumers of the
'generic-adc-thermal' node as the convention is to not have those in
the examples.
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221011175235.3191509-1-robh@kernel.orgSigned-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>