rockchip: px30: make UART pinmux accessible to TPL/SPL DTB

This adds the default pinmux for UART2 and UART5 to the TPL/SPL DTB (if
not removed through the CONFIG_OF_SPL_REMOVE_PROPS symbol) as those two
controllers are always made available to all boards.

Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>

arch/arm/dts/px30-u-boot.dtsi

@@ -33,11 +33,27 @@
 	bootph-all;
 };
 
+&uart2m0_xfer {
+	bootph-all;
+};
+
 &uart5 {
 	clock-frequency = <24000000>;
 	bootph-all;
 };
 
+&uart5_cts {
+	bootph-all;
+};
+
+&uart5_rts {
+	bootph-all;
+};
+
+&uart5_xfer {
+	bootph-all;
+};
+
 &sdmmc {
 	bootph-all;