ksefltest: MAINTAINERS git tree entry is incorrect

There is a few more subdirectories needed in the git tree path for the
linux-kselftest url in order to be able to properly clone it.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>