arm: dts: rk3399-rockpro64: slightly increase center voltage

The rk3399 VD_CENTER voltage domain is not subject to dynamic voltage
scaling. So the regulator reset voltage of 0.9V is used on this board.
Let u-boot initialize the center voltage to 0.95V as it is done for the
VD_LOGIC domain. This avoids instability and occasional linux kernel
Opses on this board.

Signed-off-by: Soeren Moch <smoch@web.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi b/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi
index a073ea2..4648513 100644
--- a/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi
@@ -11,6 +11,11 @@
 	};
 };
 
+&vdd_center {
+	regulator-min-microvolt = <950000>;
+	regulator-max-microvolt = <950000>;
+};
+
 &vdd_log {
 	regulator-init-microvolt = <950000>;
 };