These are currently created in the source directory, which is not ideal.
Move them to the persistent-data directory instead. Update the test so
skip validating the filename, since it now includes a full path.
Signed-off-by: Simon Glass <sjg@chromium.org>
Tidy this up so that pylint is happy. Use hex for the 1MB size and make
sure it is not a floating-point value.
Add a little main program to allow the code to be tried out, since at
present is only called from a long-running test.
Signed-off-by: Simon Glass <sjg@chromium.org>
