rcu: fix header guard for rcu_all_qs()

rcu_all_qs() is defined for !CONFIG_PREEMPT_RCU but the declaration
is conditioned on CONFIG_PREEMPTION.

With CONFIG_PREEMPT_LAZY, CONFIG_PREEMPTION=y does not imply
CONFIG_PREEMPT_RCU=y.

Decouple the two.

Cc: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

include/linux/rcutree.h

@@ -103,7 +103,7 @@ extern int rcu_scheduler_active;
 void rcu_end_inkernel_boot(void);
 bool rcu_inkernel_boot_has_ended(void);
 bool rcu_is_watching(void);
-#ifndef CONFIG_PREEMPTION
+#ifndef CONFIG_PREEMPT_RCU
 void rcu_all_qs(void);
 #endif