tracing: rename EVENT_TRACER config to ENABLE_EVENT_TRACING

Currently we have two configs: EVENT_TRACING and EVENT_TRACER.
All tracers enable EVENT_TRACING. The EVENT_TRACER is only a
convenience to enable the EVENT_TRACING when no other tracers
are enabled.

The names EVENT_TRACER and EVENT_TRACING are too similar and confusing.
This patch renames EVENT_TRACER to ENABLE_EVENT_TRACING to be more
appropriate to what it actually does, as well as add a comment in
the help menu to explain the option's purpose.

[ Impact: rename config option to reduce confusion ]

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/Kconfig

@@ -183,14 +183,18 @@ config CONTEXT_SWITCH_TRACER
 	  This tracer gets called from the context switch and records
 	  all switching of tasks.
 
-config EVENT_TRACER
+config ENABLE_EVENT_TRACING
 	bool "Trace various events in the kernel"
 	select TRACING
 	help
 	  This tracer hooks to various trace points in the kernel
 	  allowing the user to pick and choose which trace point they
 	  want to trace.
 
+	  Note, all tracers enable event tracing. This option is
+	  only a convenience to enable event tracing when no other
+	  tracers are selected.
+
 config FTRACE_SYSCALLS
 	bool "Trace syscalls"
 	depends on HAVE_FTRACE_SYSCALLS