kunit: test.h: fix a kernel-doc markup

Fix this kernel-doc warning:

	Documentation/dev-tools/kunit/api/test:9: ./include/kunit/test.h:323: WARNING: Inline interpreted text or phrase reference start-string without end-string.

Functions should use func_name() on kernel-doc markups, as
documented at:
	Documentation/doc-guide/kernel-doc.rst

Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>