tracing: move trace point formats to files in include/trace directory

Impact: clean up

To further facilitate the ease of adding trace points for developers, this
patch creates include/trace/trace_events.h and
include/trace/trace_event_types.h.

The former file will hold the trace/<type>.h files and the latter will hold
the trace/<type>_event_types.h files.

To create new tracepoints and to have them automatically
appear in the event tracer, a developer makes the trace/<type>.h file
which includes <linux/tracepoint.h> and the trace/<type>_event_types.h file.

The trace/<type>_event_types.h file will hold the TRACE_FORMAT
macros.

Then add the trace/<type>.h file to trace/trace_events.h,
and add the trace/<type>_event_types.h to the trace_event_types.h file.

No need to modify files elsewhere.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>