MIPS: ralink: dts: gardena_smart_gateway_mt7688: Limit UART1

The radio module asserts CTS when its RX buffer has 10 bytes left.
Putting just 8 instead of 16 bytes into the UART1 TX buffer on the Linux
side ensures to not overflow the RX buffer on the radio module side.
Signed-off-by: Reto Schneider <reto.schneider@husqvarnagroup.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Paul Burton <paul.burton@mips.com>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: linux-mips@vger.kernel.org

arch/mips/boot/dts/ralink/gardena_smart_gateway_mt7688.dts

@@ -177,6 +177,9 @@ &uart1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinmux_i2s_gpio>;		/* GPIO0..3 */
 
+	fifo-size = <8>;
+	tx-threshold = <8>;
+
 	rts-gpios = <&gpio 1 GPIO_ACTIVE_LOW>;
 	cts-gpios = <&gpio 2 GPIO_ACTIVE_LOW>;
 };