arm64: dts: qcom: Fix MPP's function used for LED control

The qcom-spmi-mpp driver is now using string "digital" to denote
old "normal" functionality. Update DTS file.
Also update the powersource.
Signed-off-by: Ivan T. Ivanov <ivan.ivanov@linaro.org>

arch/arm64/boot/dts/qcom/apq8016-sbc-pmic-pins.dtsi

@@ -33,7 +33,7 @@ &pm8916_mpps {
 	pm8916_mpps_leds: pm8916_mpps_leds {
 		pinconf {
 			pins = "mpp2", "mpp3";
-			function = PMIC_GPIO_FUNC_NORMAL;
+			function = "digital";
 			output-low;
 		};
 	};