arm64: dts: imx8mn: Adjust 1.2GHz OPP voltage to OD mode

According to latest datasheet Rev.0, 10/2019, there is restriction
as below:

"If VDD_SOC/GPU/DDR = 0.95V, then VDD_ARM must be >= 0.95V."

As by default SoC is running at OD mode(VDD_SOC = 0.95V), so
VDD_ARM 1.2GHz OPP's voltage should be increased to 0.95V.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mn.dtsi

@@ -116,7 +116,7 @@ a53_opp_table: opp-table {
 
 		opp-1200000000 {
 			opp-hz = /bits/ 64 <1200000000>;
-			opp-microvolt = <850000>;
+			opp-microvolt = <950000>;
 			opp-supported-hw = <0xb00>, <0x7>;
 			clock-latency-ns = <150000>;
 			opp-suspend;