rcu: Remove rcu_preempt_check_callbacks()

With the removal of CONFIG_TINY_PREEMPT_RCU, rcu_preempt_check_callbacks()
is now an empty function.  This commit therefore eliminates it by
inlining it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

kernel/rcutiny.c

@@ -257,7 +257,6 @@ void rcu_check_callbacks(int cpu, int user)
 		rcu_sched_qs(cpu);
 	else if (!in_softirq())
 		rcu_bh_qs(cpu);
-	rcu_preempt_check_callbacks();
 }
 
 /*

kernel/rcutiny_plugin.h

@@ -102,14 +102,6 @@ static void check_cpu_stalls(void)
 	RCU_TRACE(check_cpu_stall_preempt());
 }
 
-/*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to check.
- */
-static void rcu_preempt_check_callbacks(void)
-{
-}
-
 /*
  * Because preemptible RCU does not exist, it never has any callbacks
  * to remove.