tracing: remove unused ftrace_output_event() prototype

The prototype of ftrace_output_event was added by commit 1d6bae96
("tracing: Move raw output code from macro to standalone function")
but this function was not defined anywhere, and is still nowhere to be
found.

Link: http://lkml.kernel.org/r/1430648282-25792-1-git-send-email-nicolas.iooss_linux@m4x.org



Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>