selftests/ftrace: Return unsupported for the unconfigured features

As same as other test cases, return unsupported if kprobe_events
or argument access feature are not found.

There can be a new arch which does not port those features yet,
and an older kernel which doesn't support it.
Those can not enable the features.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>