arm64: dts: apq8096-db820c: never disable regulator on LS expansion

1.8v regulator on LS expansion should not be disabled anytime to comply
with 96boards spec. So make this explicit with always-on flag.
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi

@@ -189,9 +189,15 @@ s3 {
 					regulator-min-microvolt = <1300000>;
 					regulator-max-microvolt = <1300000>;
 				};
+
+				/**
+				 * 1.8v required on LS expansion
+				 * for mezzanine boards
+				 */
 				s4 {
 					regulator-min-microvolt = <1800000>;
 					regulator-max-microvolt = <1800000>;
+					regulator-always-on;
 				};
 				s5 {
 					regulator-min-microvolt = <2150000>;