tests: uart_async_api: Support RTXXX

Support mimxrt595_evk_cm33 and mimxrt685_evk_cm33
on the uart_async_api test with a board overlay

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
diff --git a/tests/drivers/uart/uart_async_api/boards/mimxrt595_evk_cm33.overlay b/tests/drivers/uart/uart_async_api/boards/mimxrt595_evk_cm33.overlay
new file mode 100644
index 0000000..3929742
--- /dev/null
+++ b/tests/drivers/uart/uart_async_api/boards/mimxrt595_evk_cm33.overlay
@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+dut: &flexcomm12 { };
diff --git a/tests/drivers/uart/uart_async_api/boards/mimxrt685_evk_cm33.overlay b/tests/drivers/uart/uart_async_api/boards/mimxrt685_evk_cm33.overlay
new file mode 100644
index 0000000..43f7fdf
--- /dev/null
+++ b/tests/drivers/uart/uart_async_api/boards/mimxrt685_evk_cm33.overlay
@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+dut: &flexcomm4 { };
diff --git a/tests/drivers/uart/uart_async_api/testcase.yaml b/tests/drivers/uart/uart_async_api/testcase.yaml
index d94ff3f..b54909f 100644
--- a/tests/drivers/uart/uart_async_api/testcase.yaml
+++ b/tests/drivers/uart/uart_async_api/testcase.yaml
@@ -40,7 +40,7 @@
     extra_args: DTC_OVERLAY_FILE="boards/nrf52840dk_nrf52840.overlay;boards/nrf_uart.overlay"
   drivers.uart.async_api.rtt:
     filter: CONFIG_UART_CONSOLE and CONFIG_SERIAL_SUPPORT_ASYNC and CONFIG_HAS_SEGGER_RTT
-      and not CONFIG_UART_MCUX_LPUART
+      and not CONFIG_UART_MCUX_LPUART and not CONFIG_UART_MCUX_FLEXCOMM
     extra_args: DTC_OVERLAY_FILE=boards/segger_rtt.overlay
     extra_configs:
       - CONFIG_USE_SEGGER_RTT=y