board: arm64: imx8mm_evk: add a dummy file

Because we currently use RAM_CONSOLE for now, and there is actually
no device in the build, so there is twister build failure,
add a dummy file to avoid build failure.

Signed-off-by: Peng Fan <peng.fan@nxp.com>

boards/arm64/imx8mm_evk/CMakeLists.txt

@@ -1 +1,4 @@
 # SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+zephyr_library_sources(dummy.c)

boards/arm64/imx8mm_evk/dummy.c

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2021 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef CONFIG_UART_MCUX_IUART
+
+#define DT_DRV_COMPAT nxp_imx_iuart
+
+#include <device.h>
+#include <drivers/uart.h>
+#include <drivers/clock_control.h>
+#include <errno.h>
+#include <soc.h>
+
+static int dummy_init(const struct device *dev)
+{
+	return 0;
+}
+
+#define IUART_MCUX_INIT(n)						\
+									\
+	DEVICE_DT_INST_DEFINE(n,					\
+			    &dummy_init,				\
+			    NULL,					\
+			    NULL,					\
+			    NULL,					\
+			    PRE_KERNEL_1,				\
+			    0,						\
+			    NULL);
+
+DT_INST_FOREACH_STATUS_OKAY(IUART_MCUX_INIT)
+
+#endif