doc: Tidy up the bindings for the config/ node

Sort these and add a type so it is clear how to set the value. Add a note
about usage to the top. Correct the 'no-keyboard' binding which is missing
a prefix.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
1 file changed