tracing: Have HIST_TRIGGERS select TRACING

The kbuild test robot reported a compile error if HIST_TRIGGERS was
enabled but nothing else that selected TRACING was configured in.

HIST_TRIGGERS should directly select it and not rely on anything else
to do it.

Link: http://lkml.kernel.org/r/57791866.8080505@linux.intel.comReported-by: kbuild test robot <fennguang.wu@intel.com>
Fixes: 7ef224d1 ("tracing: Add 'hist' event trigger command")
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/Kconfig

@@ -542,6 +542,7 @@ config HIST_TRIGGERS
 	bool "Histogram triggers"
 	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select TRACING_MAP
+	select TRACING
 	default n
 	help
 	  Hist triggers allow one or more arbitrary trace event fields