ARM: dts: stm32: Replace deprecated st,hw-flow-ctrl with uart-has-rtscts

Replace deprecated st,hw-flow-ctrl with uart-has-rtscts .
No functional change.
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

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

@@ -208,7 +208,7 @@ &usart3 {
 	dmas = <&dmamux1 45 0x400 0x05>,
 	       <&dmamux1 46 0x400 0x05>;
 	dma-names = "rx", "tx";
-	st,hw-flow-ctrl;
+	uart-has-rtscts;
 	status = "okay";
 
 	bluetooth {

arch/arm/boot/dts/stm32mp157a-stinger96.dtsi

@@ -287,7 +287,7 @@ &usart2 {
 	pinctrl-names = "default", "sleep";
 	pinctrl-0 = <&usart2_pins_b>;
 	pinctrl-1 = <&usart2_sleep_pins_b>;
-	st,hw-flow-ctrl;
+	uart-has-rtscts;
 	/delete-property/dmas;
 	/delete-property/dma-names;
 	status = "okay";
@@ -297,7 +297,7 @@ &usart2 {
 &uart4 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart4_pins_c>;
-	st,hw-flow-ctrl;
+	uart-has-rtscts;
 	/delete-property/dmas;
 	/delete-property/dma-names;
 	status = "okay";

arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi

@@ -452,7 +452,7 @@ &usart2 {
 	pinctrl-names = "default", "sleep";
 	pinctrl-0 = <&usart2_pins_a>;
 	pinctrl-1 = <&usart2_sleep_pins_a>;
-	st,hw-flow-ctrl;
+	uart-has-rtscts;
 	/delete-property/dmas;
 	/delete-property/dma-names;
 	status = "okay";