bridge: simplify the flush_store by calling store_bridge_parm

There are some repetitive codes in flush_store, we can remove
them by calling store_bridge_parm, also, it would send rtnl notification
after we add it in store_bridge_parm in the following patches.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Reviewed-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/br_sysfs_br.c

@@ -336,17 +336,17 @@ static ssize_t group_addr_store(struct device *d,
 
 static DEVICE_ATTR_RW(group_addr);
 
+static int set_flush(struct net_bridge *br, unsigned long val)
+{
+	br_fdb_flush(br);
+	return 0;
+}
+
 static ssize_t flush_store(struct device *d,
 			   struct device_attribute *attr,
 			   const char *buf, size_t len)
 {
-	struct net_bridge *br = to_bridge(d);
-
-	if (!ns_capable(dev_net(br->dev)->user_ns, CAP_NET_ADMIN))
-		return -EPERM;
-
-	br_fdb_flush(br);
-	return len;
+	return store_bridge_parm(d, buf, len, set_flush);
 }
 static DEVICE_ATTR_WO(flush);