tracing: clean up menu

Clean up menu structure, introduce TRACING_SUPPORT switch that signals
whether an architecture supports various instrumentation mechanisms.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/Kconfig b/arch/Kconfig
index 550dab2..a092dc7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -6,6 +6,7 @@
 	tristate "OProfile system profiling (EXPERIMENTAL)"
 	depends on PROFILING
 	depends on HAVE_OPROFILE
+	depends on TRACING_SUPPORT
 	select TRACING
 	select RING_BUFFER
 	help