cmd: bind: Try to improve the (un)bind help

cmd: bind: Try to improve the (un)bind help

While it may sound totally obvious for the regular U-Boot developer to
get the parameters of the bind/unbind commands from the output of 'dm
tree', it did not felt straightforward to me until I was explicitly
told to look there. And even when I knew the command, I did not make a
direct link between the arguments of this command and the columns
returned by 'dm tree'.

Several of us lost a lot of time because of that, I would like to kindly
help other users by slightly improving this textual line. Unfortunately,
because of how this string is used (like within the 'help' command) I
cannot detail much more, but at least the pointer is there.

While we add this message, we can also imply CMD_DM when we enable
CMD_BIND so the debug message does not lead to an unknown command. This
way the 'dm' command will likely be there unless explicitly disabled.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20231010090304.49335-3-miquel.raynal@bootlin.com
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>