regulator: dt-bindings: richtek,rt4801: use existing ena_gpiod feature

The binding and driver duplicated regulator core feature of controlling
regulators with GPIOs (of_parse_cb + ena_gpiod) and created its own
enable-gpios property with multiple GPIOs.

This is a less preferred way, because enable-gpios should enable only one
element, not multiple. It also duplicates existing solution.

Deprecate the original 'enable-gpios' and add per-regulator property.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220425072455.27356-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>