ARM: dts: stm32: Enable RTS/CTS for DH AV96 UART7

The DH AV96 has RTS/CTS lines available on UART7, describe them in DT.

Signed-off-by: Marek Vasut <[e-mail]>
Cc: Alexandre Torgue <[e-mail]>
Cc: Maxime Coquelin <[e-mail]>
Cc: Patrice Chotard <[e-mail]>
Cc: Patrick Delaunay <[e-mail]>
Cc: [e-mail]
To: [e-mail]
Signed-off-by: Alexandre Torgue <[e-mail]>

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

···
 	label = "LS-UART0";
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart7_pins_a>;
+	uart-has-rtscts;
 	status = "okay";
 };