rcu: Move RCU_TRACE to lib/Kconfig.debug

The RCU_TRACE kernel parameter has always been intended for debugging,
not for production use.  Formalize this by moving RCU_TRACE from
init/Kconfig to lib/Kconfig.debug.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8745ac7..3cc419d0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -927,6 +927,16 @@
 
 	  Say Y if you want to enable such checks.
 
+config RCU_TRACE
+	bool "Enable tracing for RCU"
+	depends on DEBUG_KERNEL
+	help
+	  This option provides tracing in RCU which presents stats
+	  in debugfs for debugging RCU implementation.
+
+	  Say Y here if you want to enable RCU tracing
+	  Say N if you are unsure.
+
 config KPROBES_SANITY_TEST
 	bool "Kprobes sanity tests"
 	depends on DEBUG_KERNEL