dt-bindings: leds: pca955x: Convert text bindings to YAML

Convert the text bindings of pca955x to YAML so it could be used to
validate the DTS.

Signed-off-by: Ricky CX Wu <ricky.cx.wu.wiwynn@gmail.com>
Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20241016093857.925467-1-Delphine_CC_Chiu@wiwynn.com


Signed-off-by: Lee Jones <lee@kernel.org>