tests: drivers: uart_async_api: fix userspace fault

Updated driver to add missing configuration during
init while using async APIs.

Updated overlay and conf files for mimxrt1064
to run outside of usersapce mode to avoid
inaccessible memory regions when using nocache.

drivers/serial/uart_mcux_lpuart.c

@@ -1090,6 +1090,23 @@ static int mcux_lpuart_configure_init(const struct device *dev, const struct uar
 		return ret;
 	}
 
+#ifdef CONFIG_UART_ASYNC_API
+	uart_config.rxIdleType = kLPUART_IdleTypeStopBit;
+	uart_config.rxIdleConfig = kLPUART_IdleCharacter1;
+	data->async.next_rx_buffer = NULL;
+	data->async.next_rx_buffer_len = 0;
+	data->async.uart_dev = dev;
+	k_work_init_delayable(&data->async.rx_dma_params.timeout_work,
+			      mcux_lpuart_async_rx_timeout);
+	k_work_init_delayable(&data->async.tx_dma_params.timeout_work,
+			      mcux_lpuart_async_tx_timeout);
+
+	/* Disable the UART Receiver until the async API provides a buffer to
+	 * to receive into with rx_enable
+	 */
+	uart_config.enableRx = false;
+#endif
+
 	LPUART_Init(config->base, &uart_config, clock_freq);
 
 	if (cfg->flow_ctrl == UART_CFG_FLOW_CTRL_RS485) {

tests/drivers/uart/uart_async_api/boards/mimxrt1064_evk.conf

@@ -0,0 +1,2 @@
+# Userspace is unable to access the nocache region.
+CONFIG_USERSPACE=n

tests/drivers/uart/uart_async_api/boards/mimxrt1064_evk.overlay

@@ -1,11 +1,5 @@
 /* SPDX-License-Identifier: Apache-2.0 */
 
-/ {
-	chosen {
-		zephyr,sram = &dtcm;
-	};
-};
-
 dut: &lpuart3 {
 	status = "okay";
 	current-speed = <115200>;