dt-bindings: trivial-devices: add isil,isl69269

The ISL69269 is a PMBus voltage regulator with no configurable
parameters.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240502002836.17862-6-zev@bewilderbeest.net


Signed-off-by: Joel Stanley <joel@jms.id.au>