arm64: dts: qcom: pm8550: add flash LED controller

Add node for PM8550 PMIC flash LED controller.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230516150202.188655-2-krzysztof.kozlowski@linaro.org