Document the bdinfo -a, -e and -m options in the long help, but only
when they can be used. The string concatenation is a bit odd with two
newlines, but it does render properly once in U-Boot CLI.
Tested-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
de3754fea3