ARM: dts: rockchip: Add ramp delay for vdd_cpu in firefly board dts

Adds ramp delay for the vdd_cpu output. It removes warning "ramp_delay
not set" emitted by the function regulator_set_voltage_time_sel() by the
same time, which floods kernel logs.
Signed-off-by: NRomain Perier <romain.perier@gmail.com>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288-firefly.dtsi

@@ -213,6 +213,8 @@
 		regulator-max-microvolt = <1350000>;
 		regulator-always-on;
 		regulator-boot-on;
+		regulator-enable-ramp-delay = <300>;
+		regulator-ramp-delay = <8000>;
 		vin-supply = <&vcc_sys>;
 	};