arm64: dts: rockchip: Enable UART6 on rock-5b

Enable UART lines on Radxa ROCK 5 Model B M.2 Key E.
Signed-off-by: Tamás Szűcs <szucst@iit.uni-miskolc.hu>
Link: https://lore.kernel.org/r/20231013215208.81345-1-szucst@iit.uni-miskolc.huSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts

@@ -377,6 +377,12 @@ &sdio {
 	status = "okay";
 };
 
+&uart6 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&uart6m1_xfer &uart6m1_ctsn &uart6m1_rtsn>;
+	status = "okay";
+};
+
 &spi2 {
 	status = "okay";
 	assigned-clocks = <&cru CLK_SPI2>;