dt-bindings: hwmon (pwm-fan) Remove dead "cooling-*-state" properties

dt-bindings: hwmon (pwm-fan) Remove dead "cooling-*-state" properties

The old "cooling-{min,max}-state" properties for thermal bindings were
ratified to "cooling-{min,max}-level" by commit eb168b70dea5 ("of:
thermal: Fix inconsitency between cooling-*-state and cooling-*-level"),
which were later removed entirely by commit e04907dbc259 ("dt-bindings:
thermal: Remove "cooling-{min|max}-level" properties").

The pwm-fan binding, however, was apparently in-flight in parallel with
that ratification, and so managed to introduce an example of the old
properties which escaped the scope of the later cleanup and has thus
continued to be dutifully copied for new boards despite being useless.
Clean up these remaining undocumented anachronisms to minimise any
further confusion.

Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>