samples: drivers: uart: async_api: Added support for BTL-s

Added support for async api application on BTL-s platform

Signed-off-by: Anisetti Avinash Krishna <anisetti.avinash.krishna@intel.com>

Author: akanisetti

samples/drivers/uart/async_api/boards/intel_btl_s_crb.conf

@@ -0,0 +1 @@
+CONFIG_UART_INTERRUPT_DRIVEN=y

samples/drivers/uart/async_api/boards/intel_btl_s_crb.overlay

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2025 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&uart0{
+	status = "okay";
+};
+&uart0_dma{
+	status ="okay";
+};
+/{
+	chosen {
+		zephyr,console = &uart0;
+		zephyr,shell-uart = &uart0;
+	};
+};