rcu: Make rcu_gp_cleanup() be noinline for tracing

Although there are trace events for RCU grace periods, these are only
enabled in CONFIG_RCU_TRACE=y kernels.  This commit therefore marks
rcu_gp_cleanup() noinline in order to provide a function that can be
traced that is invoked near the end of each grace period.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree.c

@@ -2026,7 +2026,7 @@ static void rcu_gp_fqs_loop(void)
 /*
  * Clean up after the old grace period.
  */
-static void rcu_gp_cleanup(void)
+static noinline void rcu_gp_cleanup(void)
 {
 	int cpu;
 	bool needgp = false;