selftests/harness: Clean up kern-doc for fixtures

 *

 * .. code-block:: c

 *

 *     FIXTURE_DATA(datatype name)

 *     FIXTURE_DATA(datatype_name)

 *

 * Almost always, you want just FIXTURE() instead (see below).

 * This call may be used when the type of the fixture data

 * is needed.  In general, this should not be needed unless

 * the *self* is being passed to a helper directly.

 *

 * .. code-block:: c

 *

 *     FIXTURE(datatype name) {

 *     FIXTURE(fixture_name) {

 *       type property1;

 *       ...

 *     };

 *

 * .. code-block:: c

 *

 *     FIXTURE_SETUP(fixture name) { implementation }

 *     FIXTURE_SETUP(fixture_name) { implementation }

 *

 * Populates the required "setup" function for a fixture.  An instance of the

 * datatype defined with FIXTURE_DATA() will be exposed as *self* for the

 *

 * .. code-block:: c

 *

 *     FIXTURE_TEARDOWN(fixture name) { implementation }

 *     FIXTURE_TEARDOWN(fixture_name) { implementation }

 *

 * Populates the required "teardown" function for a fixture.  An instance of the

 * datatype defined with FIXTURE_DATA() will be exposed as *self* for the

 *

 * .. code-block:: c

 *

 *     FIXTURE_VARIANT(datatype name) {

 *     FIXTURE_VARIANT(fixture_name) {

 *       type property1;

 *       ...

 *     };

 *

 * .. code-block:: c

 *

 *     FIXTURE_ADD(datatype name) {

 *       .property1 = val1;

 *     FIXTURE_VARIANT_ADD(fixture_name, variant_name) {

 *       .property1 = val1,

 *       ...

 *     };

 *