CI: Run code-coverage test for Binman

CI: Run code-coverage test for Binman

Binman includes a good set of tests covering all of its functionality.
This includes a code-coverage test.

However to date the code-coverage test has not been checked
automatically by CI, relying on people to run 'binman test -T'
themselves.

Plug the gap to avoid bugs creeping in future.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>