ftrace: Replace uses of _ftrace_direct APIs with _ftrace_direct_multi

The _multi API requires that users keep their own ops but can enforce
that an op is only associated to one direct call.

Link: https://lkml.kernel.org/r/20230321140424.345218-3-revest@chromium.org

Signed-off-by: Florent Revest <revest@chromium.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>