arm64: dts: exynos: Modify the voltage range for BUCK2 for exynos7

Change the BUCK2 (vdd_atlas) voltage range to '500 - 1200mv' since
CPU DVFS requires it.
Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

arch/arm64/boot/dts/exynos/exynos7-espresso.dts

@@ -249,7 +249,7 @@ buck1_reg: BUCK1 {
 
 			buck2_reg: BUCK2 {
 				regulator-name = "vdd_atlas";
-				regulator-min-microvolt = <1200000>;
+				regulator-min-microvolt = <500000>;
 				regulator-max-microvolt = <1200000>;
 				regulator-always-on;
 				regulator-boot-on;