ARM: dts: kzm9g: SCIFA4 supports RTS/CTS hardware flow control

On the KZM-A9-GT development board, the RTS and CTS pins of the debug
console SCIFA4 are wired to the CP2102 Serial-USB bridge.  Reflect
this in the DTS by adding the "uart-has-rtscts" property to the scifa4
device node.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/sh73a0-kzm9g.dts

@@ -378,6 +378,7 @@
 	pinctrl-0 = <&scifa4_pins>;
 	pinctrl-names = "default";
 
+	uart-has-rtscts;
 	status = "okay";
 };