imx8mm_beacon: Switch to binman for generating image

To eliminate a warning when using custom imx tools for generating
a binary, use binman to generate flash.bin.

Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
6 files changed