ARM: dts: Add missing op_mode property to PMIC on Arndale

Though the default value is 1, add it explicitly to avoid
unnecessary boot warnings and for consistency.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos5250-arndale.dts

@@ -302,11 +302,13 @@ buck5_reg: BUCK5 {
 				buck7_reg: BUCK7 {
 					regulator-name = "PVDD_BUCK7";
 					regulator-always-on;
+					op_mode = <1>;
 				};
 
 				buck8_reg: BUCK8 {
 					regulator-name = "PVDD_BUCK8";
 					regulator-always-on;
+					op_mode = <1>;
 				};
 
 				buck9_reg: BUCK9 {