ARM: dts: stm32h7-pinctrl: add _a suffix to u[s]art_pins phandles

Allow expanding possible configurations for the same peripheral,
consistent with the scheme adopted in Linux.

Signed-off-by: Dario Binacchi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Torgue <[e-mail]>

arch/arm/boot/dts/st/stm32h7-pinctrl.dtsi

···
 		};
 	};
 
-	uart4_pins: uart4-0 {
+	uart4_pins_a: uart4-0 {
 		pins1 {
 			pinmux = <STM32_PINMUX('A', 0, AF8)>; /* UART4_TX */
 			bias-disable;
···
 		};
 	};
 
-	usart1_pins: usart1-0 {
+	usart1_pins_a: usart1-0 {
 		pins1 {
 			pinmux = <STM32_PINMUX('B', 14, AF4)>; /* USART1_TX */
 			bias-disable;
···
 		};
 	};
 
-	usart2_pins: usart2-0 {
+	usart2_pins_a: usart2-0 {
 		pins1 {
 			pinmux = <STM32_PINMUX('D', 5, AF7)>; /* USART2_TX */
 			bias-disable;
···
 		};
 	};
 
-	usart3_pins: usart3-0 {
+	usart3_pins_a: usart3-0 {
 		pins1 {
 			pinmux = <STM32_PINMUX('B', 10, AF7)>, /* USART3_TX */
 				 <STM32_PINMUX('D', 12, AF7)>; /* USART3_RTS_DE */

arch/arm/boot/dts/st/stm32h743i-disco.dts

···
 };
 
 &usart2 {
-	pinctrl-0 = <&usart2_pins>;
+	pinctrl-0 = <&usart2_pins_a>;
 	pinctrl-names = "default";
 	status = "okay";
 };

arch/arm/boot/dts/st/stm32h743i-eval.dts

···
 };
 
 &usart1 {
-	pinctrl-0 = <&usart1_pins>;
+	pinctrl-0 = <&usart1_pins_a>;
 	pinctrl-names = "default";
 	status = "okay";
 };

arch/arm/boot/dts/st/stm32h750i-art-pi.dts

···
 };
 
 &usart2 {
-	pinctrl-0 = <&usart2_pins>;
+	pinctrl-0 = <&usart2_pins_a>;
 	pinctrl-names = "default";
 	status = "disabled";
 };
 
 &usart3 {
 	pinctrl-names = "default";
-	pinctrl-0 = <&usart3_pins>;
+	pinctrl-0 = <&usart3_pins_a>;
 	dmas = <&dmamux1 45 0x400 0x05>,
 	       <&dmamux1 46 0x400 0x05>;
 	dma-names = "rx", "tx";
···
 };
 
 &uart4 {
-	pinctrl-0 = <&uart4_pins>;
+	pinctrl-0 = <&uart4_pins_a>;
 	pinctrl-names = "default";
 	status = "okay";
 };