imx8mn_beacon: Fix booting hang and switch to binman

Somewhere along the line, the board stopped being able to boot.
Rather than just fixing the issue, let's fix the issue and migrate
to binman to eliminate a warning when using custom imx tools for
generating the binary.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
diff --git a/board/beacon/imx8mn/imximage-8mn-lpddr4.cfg b/board/beacon/imx8mn/imximage-8mn-lpddr4.cfg
new file mode 100644
index 0000000..7286b26
--- /dev/null
+++ b/board/beacon/imx8mn/imximage-8mn-lpddr4.cfg
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2021 NXP
+ */
+
+#define __ASSEMBLY__
+
+ROM_VERSION	v2
+BOOT_FROM	sd
+LOADER		u-boot-spl-ddr.bin	0x912000