[nrf fromtree] tests: drivers: uart: Add support test uart_async for ek_ra8p1

Add support test uart_async_api for Renesas ek_ra8p1

Signed-off-by: Khoa Nguyen <[email protected]>
(cherry picked from commit e6f9cd3)

Author: khoa-nguyen-18

tests/drivers/uart/uart_async_api/boards/ek_ra8p1_r7ka8p1kflcac_cm85.overlay

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&pinctrl {
+	sci2_default: sci2_default {
+		group1 {
+			/* tx */
+			psels = <RA_PSEL(RA_PSEL_SCI_2, 8, 1)>;
+			drive-strength = "medium";
+		};
+
+		group2 {
+			/* rx */
+			psels = <RA_PSEL(RA_PSEL_SCI_2, 8, 2)>;
+		};
+	};
+};
+
+&sci2 {
+	interrupts = <30 1>, <31 1>, <32 1>, <33 1>;
+	interrupt-names = "rxi", "txi", "tei", "eri";
+	pinctrl-0 = <&sci2_default>;
+	pinctrl-names = "default";
+	status = "okay";
+
+	dut: uart {
+		current-speed = <115200>;
+		status = "okay";
+	};
+};