net: update comment for netif_dormant() function

This patch updates the comment for netif_dormant() function to reflect
the intended usage.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -3408,10 +3408,10 @@ static inline void netif_dormant_off(struct net_device *dev)
 }
 
 /**
- *	netif_dormant - test if carrier present
+ *	netif_dormant - test if device is dormant
  *	@dev: network device
  *
- * Check if carrier is present on device
+ * Check if device is dormant.
  */
 static inline bool netif_dormant(const struct net_device *dev)
 {