arm64: dts: actions: s900-bubblegum-96: Add fake uart5 clock

Give the serial driver a fixed-clock as input for baudrate 115200.
Signed-off-by: Andreas Färber <afaerber@suse.de>

arch/arm64/boot/dts/actions/s900-bubblegum-96.dts

@@ -24,6 +24,12 @@ memory@0 {
 		device_type = "memory";
 		reg = <0x0 0x0 0x0 0x80000000>;
 	};
+
+	uart5_clk: uart5-clk {
+		compatible = "fixed-clock";
+		clock-frequency = <921600>;
+		#clock-cells = <0>;
+	};
 };
 
 &timer {
@@ -32,4 +38,5 @@ &timer {
 
 &uart5 {
 	status = "okay";
+	clocks = <&uart5_clk>;
 };