rcuclassic: fix compiler warning

CC      kernel/rcuclassic.o
kernel/rcuclassic.c: In function 'rcu_init_percpu_data':
kernel/rcuclassic.c:705: warning: comparison of distinct pointer types lacks a cast
kernel/rcuclassic.c:713: warning: comparison of distinct pointer types lacks a cast

flags should be unsigned long.
Signed-off-by: NHiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/rcuclassic.c

@@ -714,7 +714,7 @@ void rcu_check_callbacks(int cpu, int user)
 static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
 						struct rcu_data *rdp)
 {
-	long flags;
+	unsigned long flags;
 
 	spin_lock_irqsave(&rcp->lock, flags);
 	memset(rdp, 0, sizeof(*rdp));