rockchip: firefly-rk3399: Provide init voltage

Add missing regulator-init-microvolt property to vdd_log regulator.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3399-firefly-u-boot.dtsi b/arch/arm/dts/rk3399-firefly-u-boot.dtsi
index 38e0897..c58ad95 100644
--- a/arch/arm/dts/rk3399-firefly-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-firefly-u-boot.dtsi
@@ -11,3 +11,7 @@
 		u-boot,spl-boot-order = "same-as-spl", &sdhci, &sdmmc;
 	};
 };
+
+&vdd_log {
+	regulator-init-microvolt = <950000>;
+};