patman: Update defaults in subparsers

patman: Update defaults in subparsers

At present values from the settings file are only applied to the main
parser. With the new parser structure this means that some settings are
ignored.

Update the implementation to set defaults across the main parser and all
subparsers. Also fix up the comments, since ArgumentParser is being used
now.

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