tests: serial: Add overlay for RSK-RX130@512KB board

Add uart property in tests/uart/uart_async_api for test
async APIs on RSK-RX130-512KB board.

Signed-off-by: Phi Tran <phi.tran.jg@bp.renesas.com>

Author: Phi Tran

tests/drivers/uart/uart_async_api/boards/rsk_rx130_512kb.conf

@@ -0,0 +1 @@
+CONFIG_SYS_CLOCK_TICKS_PER_SEC=1000

tests/drivers/uart/uart_async_api/boards/rsk_rx130_512kb.overlay

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&pinctrl {
+	sci5_default: sci5_default {
+		group1 {
+			psels = <RX_PSEL(RX_PSEL_PAnPFS_TXD5, 10, 4)>,
+			<RX_PSEL(RX_PSEL_PAnPFS_RXD5, 10, 2)>;
+		};
+	};
+};
+
+&sci5 {
+	pinctrl-0 = <&sci5_default>;
+	pinctrl-names = "default";
+	status = "okay";
+	dut: uart {
+		current-speed = <115200>;
+		status = "okay";
+	};
+};