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/arch/arm/mach-imx/imx8m/Kconfig b/arch/arm/mach-imx/imx8m/Kconfig
index a2822f8..0d27912 100644
--- a/arch/arm/mach-imx/imx8m/Kconfig
+++ b/arch/arm/mach-imx/imx8m/Kconfig
@@ -124,6 +124,7 @@
 
 config TARGET_IMX8MN_BEACON
 	bool "imx8mn Beacon Embedded devkit"
+	select BINMAN
 	select IMX8MN
 	select SUPPORT_SPL
 	select IMX8M_LPDDR4