uboot-imx

main: Fix typos and checkpatch warnings in command line reading

There are a few over-long lines and other checkpatch problems in this area
of the code. Prepare the ground for the next patch by tidying these up.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>