Nothing sets function_trace_stop to disable function tracing anymore.
Remove the check for it in the arch code.

Link: http://lkml.kernel.org/r/53C8D82B.4030204@monstr.euTested-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>