imx8mm_evk: switch to use binman to pack images

Use binman to pack images

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/board/freescale/imx8mm_evk/imximage-8mm-lpddr4.cfg b/board/freescale/imx8mm_evk/imximage-8mm-lpddr4.cfg
new file mode 100644
index 0000000..b89092a
--- /dev/null
+++ b/board/freescale/imx8mm_evk/imximage-8mm-lpddr4.cfg
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2021 NXP
+ */
+
+#define __ASSEMBLY__
+
+BOOT_FROM	sd
+LOADER		mkimage.flash.mkimage	0x7E1000