tracing: Rename trace/ftrace.h to trace/trace_events.h

The name "ftrace" really refers to the function hook infrastructure. It
is not about the TRACE_EVENT() macros. The file trace/ftrace.h was originally
written to be mostly focused toward the "ftrace" code (that in kernel/trace/)
but ended up being generic and used by perf and others.

Rename the file to be less confusing about what infrastructure it belongs to.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/trace/define_trace.h

@@ -87,7 +87,7 @@
 #define DECLARE_TRACE(name, proto, args)
 
 #ifdef CONFIG_EVENT_TRACING
-#include <trace/ftrace.h>
+#include <trace/trace_events.h>
 #endif
 
 #undef TRACE_EVENT