ARM: dts: aspeed: mtmitchell: Enable the BMC UART8 and UART9

The BMC UART8 and UART9 were connected to the Secpro and Mpro console
of socket S1 on the Mt.Mitchell system.
Signed-off-by: Chanh Nguyen <chanh@os.amperecomputing.com>
Link: https://lore.kernel.org/r/20230620092537.20007-2-chanh@os.amperecomputing.comSigned-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed/aspeed-bmc-ampere-mtmitchell.dts

@@ -10,6 +10,11 @@ / {
 	model = "Ampere Mt.Mitchell BMC";
 	compatible = "ampere,mtmitchell-bmc", "aspeed,ast2600";
 
+	aliases {
+		serial7 = &uart8;
+		serial8 = &uart9;
+	};
+
 	chosen {
 		stdout-path = &uart5;
 	};
@@ -307,6 +312,14 @@ &uart4 {
 	status = "okay";
 };
 
+&uart8 {
+	status = "okay";
+};
+
+&uart9 {
+	status = "okay";
+};
+
 &i2c0 {
 	status = "okay";