moveconfig: Add an option to commit changes

moveconfig: Add an option to commit changes

The moveconfig tool is quite clever and generally produces results that
are suitable for sending as a patch without further work. The main required
step is to add the changes to a commit.

Add an option to do this automatically. This allows moveconfig to be used
from a script to convert multiple CONFIG options, once per commit.

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