markers: auto enable tracepoints (new API : trace_mark_tp())

Impact: new API

Add a new API trace_mark_tp(), which declares a marker within a
tracepoint probe. When the marker is activated, the tracepoint is
automatically enabled.

No branch test is used at the marker site, because it would be a
duplicate of the branch already present in the tracepoint.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/init/Kconfig b/init/Kconfig
index 86b00c5..f5bacb4 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -808,6 +808,7 @@
 
 config MARKERS
 	bool "Activate markers"
+	depends on TRACEPOINTS
 	help
 	  Place an empty function call at each marker site. Can be
 	  dynamically changed for a probe function.