While our version is better, it is tricky to use it when we are trying
to package things with pip. Drop it.

Somewhat reduced functionality is provided by the upstream version[1],
along with a rather annoying message each time it is used[2] [3].

[1] pip install concurrencytest
[2] https://github.com/cgoldberg/concurrencytest/issues/12
[3] https://github.com/cgoldberg/concurrencytest/pull/14

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

Remove incorrect indentation.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

At present the tests run one after the other using a single CPU. This is
not very efficient. Bring in the concurrencytest module and run the tests
concurrently, using one process for each CPU by default. A -P option
allows this to be overridden, which is necessary for code-coverage to
function correctly.

This requires fixing a few tests which are currently not fully
independent.

At some point we might consider doing this across all pytests in U-Boot.
There is a pytest version that supports specifying the number of processes
to use, but it did not work for me.

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