tracing: create menuconfig for tracing infrastructure

During testing we often use randconfig to test various kernels.
The current configuration set up does not give an easy way to disable
all tracing with a single config. The case where randconfig would
test all tracing disabled is very unlikely.

This patch adds a config option to enable or disable all tracing.
It is hooked into the tracing menu just like other submenus are done.

[ Impact: allow randconfig to easily produce all traces disabled ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/Kconfig

@@ -77,7 +77,12 @@ config TRACING_SUPPORT
 
 if TRACING_SUPPORT
 
-menu "Tracers"
+menuconfig FTRACE
+	bool "Tracers"
+	help
+	 Enable the kernel tracing infrastructure.
+
+if FTRACE
 
 config FUNCTION_TRACER
 	bool "Kernel Function Tracer"
@@ -462,7 +467,7 @@ config MMIOTRACE_TEST
 
 	  Say N, unless you absolutely know what you are doing.
 
-endmenu
+endif # FTRACE
 
 endif # TRACING_SUPPORT