selftests: ksft: Fix finished() helper exit code on skipped tests

selftests: ksft: Fix finished() helper exit code on skipped tests

The Python finished() helper currently exits with KSFT_FAIL when there
are only passed and skipped tests. Fix the logic to exit with KSFT_PASS
instead, making it consistent with its C and bash counterparts
(ksft_finished() and ktap_finished() respectively).

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Fixes: dacf1d7a78bf ("kselftest: Add test to verify probe of devices from discoverable buses")
Signed-off-by: Laura Nao <laura.nao@collabora.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>