doc: dev-tools: kselftest.rst: update config file location

Config fragment files should be placed in
tools/testing/selftests/<testdir>/config
Signed-off-by: NAnders Roxell <anders.roxell@linaro.org>
Acked-by: NShuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/kselftest.rst

@@ -159,7 +159,7 @@ Contributing new tests (details)
  * If a test needs specific kernel config options enabled, add a config file in
    the test directory to enable them.
 
-   e.g: tools/testing/selftests/android/ion/config
+   e.g: tools/testing/selftests/android/config
 
 Test Harness
 ============