test: Update command test to use unit-test functions

Rather than enabled DEBUG and using assert(), use the unit-test
functions now provided.

Drop a check that causes pytest to fail.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Rini <trini@konsulko.com> # rpi_3, rpi_4, rpi_arm64, am64x_evm_a53, am64-sk
1 file changed