[IPV4]: RT_CACHE_STAT_INC() warning fix

BUG: using smp_processor_id() in preemptible [00000001] code: rpc.statd/2408

And it _is_ a bug, but I guess we don't care enough to add preempt_disable().
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/route.c

@@ -241,7 +241,8 @@ static int			rt_hash_log;
 static unsigned int		rt_hash_rnd;
 
 static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
-#define RT_CACHE_STAT_INC(field) (__get_cpu_var(rt_cache_stat).field++)
+#define RT_CACHE_STAT_INC(field) \
+	(per_cpu(rt_cache_stat, raw_smp_processor_id()).field++)
 
 static int rt_intern_hash(unsigned hash, struct rtable *rth,
 				struct rtable **res);