ARM: dts: stm32: clean uart aliases on stm32mp15xx-dkx boards

Remove duplicates and clean uart aliases.
Uart aliases and uart pins should be declared and associated to
uart instance at the same time.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm/boot/dts/stm32mp157a-dk1.dts

@@ -17,9 +17,6 @@
 
 	aliases {
 		ethernet0 = &ethernet0;
-		serial0 = &uart4;
-		serial1 = &usart3;
-		serial2 = &uart7;
 	};
 
 	chosen {

arch/arm/boot/dts/stm32mp157c-dk2.dts

@@ -18,9 +18,6 @@
 
 	aliases {
 		ethernet0 = &ethernet0;
-		serial0 = &uart4;
-		serial1 = &usart3;
-		serial2 = &uart7;
 		serial3 = &usart2;
 	};
 

arch/arm/boot/dts/stm32mp15xx-dkx.dtsi

@@ -8,6 +8,12 @@
 #include <dt-bindings/mfd/st,stpmic1.h>
 
 / {
+	aliases {
+		serial0 = &uart4;
+		serial1 = &usart3;
+		serial2 = &uart7;
+	};
+
 	memory@c0000000 {
 		device_type = "memory";
 		reg = <0xc0000000 0x20000000>;