sparc/oprofile: Convert timer_stop() to use synchronize_rcu()

Now that synchronize_rcu() waits for preempt-disable regions of code
in addition to explicitly marked RCU read-side critical sections,
synchronize_rcu() can be used in place of synchronize_sched().  This
commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Robert Richter <rric@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: <oprofile-list@lists.sf.net>
Cc: <sparclinux@vger.kernel.org>

arch/sparc/oprofile/init.c

@@ -53,7 +53,7 @@ static void timer_stop(void)
 {
 	nmi_adjust_hz(1);
 	unregister_die_notifier(&profile_timer_exceptions_nb);
-	synchronize_sched();  /* Allow already-started NMIs to complete. */
+	synchronize_rcu();  /* Allow already-started NMIs to complete. */
 }
 
 static int op_nmi_timer_init(struct oprofile_operations *ops)