netdevice: add the case if dev is NULL

Add the case if dev is NULL in dev_{put, hold}, so the caller doesn't
need to care whether dev is NULL or not.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Yajun Deng

include/linux/netdevice.h

@@ -4143,11 +4143,13 @@ void netdev_run_todo(void);
  */
 static inline void dev_put(struct net_device *dev)
 {
+	if (dev) {
 #ifdef CONFIG_PCPU_DEV_REFCNT
-	this_cpu_dec(*dev->pcpu_refcnt);
+		this_cpu_dec(*dev->pcpu_refcnt);
 #else
-	refcount_dec(&dev->dev_refcnt);
+		refcount_dec(&dev->dev_refcnt);
 #endif
+	}
 }
 
 /**
@@ -4158,11 +4160,13 @@ static inline void dev_put(struct net_device *dev)
  */
 static inline void dev_hold(struct net_device *dev)
 {
+	if (dev) {
 #ifdef CONFIG_PCPU_DEV_REFCNT
-	this_cpu_inc(*dev->pcpu_refcnt);
+		this_cpu_inc(*dev->pcpu_refcnt);
 #else
-	refcount_inc(&dev->dev_refcnt);
+		refcount_inc(&dev->dev_refcnt);
 #endif
+	}
 }
 
 /* Carrier loss detection, dial on demand. The functions netif_carrier_on