Currently the USB tests take around two seconds to run. Remove these
unnecessary time delays so that the tests run quickly.
Signed-off-by: NSimon Glass <sjg@chromium.org>

Separate the ability to define tests and assert status of test functions
from the dm tests so they can be used more consistently throughout all
tests.
Signed-off-by: NJoe Hershberger <joe.hershberger@ni.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>

This adds a simple test for probing and a functional test using the flash
stick emulator, which tests a large chunk of the USB stack.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NMarek Vasut <marex@denx.de>