tracing: Rename ftrace_output functions to trace_output

The name "ftrace" really refers to the function hook infrastructure. It
is not about the trace_events. The ftrace_output_*() and ftrace_raw_output_*()
functions represent the trace_event code. Rename them to just trace_output
or trace_raw_output.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>