scripts: imx-usb-loader: split off topic-code into functions
Improve code understandability: extract the "jump application" Serial
Download Protocol access method and file-to-buffer reader functionality
out of do_irom_download().
Signed-off-by: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>