ARM: dts: set ramp delay for vdd_cpu

we should set it if you use dvs

pick from a8df1fc

Change-Id: I788123c611acf0dedf3de0307c08263f3c912a1c

Author: Andy3Kuo

arch/arm/boot/dts/rk3288-tinker-board.dts

@@ -392,6 +392,7 @@
 				regulator-min-microvolt = <750000>;
 				regulator-max-microvolt = <1400000>;
 				regulator-name = "vdd_arm";
+				regulator-ramp-delay = <6000>;
 				regulator-state-mem {
 					regulator-off-in-suspend;
 				};