of: Add of_phandle_args_equal() helper

Add a helper comparing two "struct of_phandle_args" to avoid
reinventing the wheel.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240129115216.96479-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>