dtoc: Add an 'all' command

With upcoming changes, dtoc will output several files for different
of-platdata components.

Add a way to output all ava!ilable files at once ('all'), to the
appropriate directories, without needing to specify each one invidually.

This puts the commands in alphabetical order, so update the tests
accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>