selftests: kselftest framework: add API to return pass/fail/* counts

Some tests print final pass/fail message based on fail count. Add
ksft_get_*_cnt() API to kselftest framework to return counts.

Update ksft_print_cnts() to print the test results summary message with
individual pass, fail, ... counters.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>