tracing: consolidate trace and trace_event headers

tracing: consolidate trace and trace_event headers

Impact: clean up

Neil Horman (et. al.) criticized the way the trace events were broken up
into two files. The reason for that was that ftrace needed to separate out
the declarations from where the #include <linux/tracepoint.h> was used.
It then dawned on me that the tracepoint.h header only needs to define the
TRACE_EVENT macro if it is not already defined.

The solution is simply to test if TRACE_EVENT is defined, and if it is not
then the linux/tracepoint.h header can define it. This change consolidates
all the <traces>.h and <traces>_event_types.h into the <traces>.h file.

Reported-by: Neil Horman <[email protected]>
Reported-by: Theodore Tso <[email protected]>
Reported-by: Jiaying Zhang <[email protected]>
Cc: Zhaolei <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>