popt: add ptest

popt: add ptest

Add a ptest for popt to core-image-ptest-all. Provide a patch to popt to
adopt the test format to "simple test" and a script for running the test.
All tests passed on a trial run.

Signed-off-by: Simone Weiss <simone.weiss@elektrobit.com>
Signed-off-by: David Niederpruem <david.niederpruem@elektrobit.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>