selftests:modify the incorrect print format

when the argument type is 'unsigned int',printf '%u'
in format string. Problem found during code reading.

Update commit log with information on how the problem
was found:
Shuah Khan <skhan@linuxfoundation.org>

Signed-off-by: zhujun2 <zhujun2@cmss.chinamobile.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>