net: add netif_napi_del function to allow for removal of napistructs

Adds netif_napi_del function which is used to remove the napi struct from
the netdev napi_list in cases where CONFIG_NETPOLL was enabled.
The motivation for adding this is to handle the case in which the number of
queues on a device changes due to a configuration change.  Previously the
napi structs for each queue would be left in the list until the netdev was
freed.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

include/linux/netdevice.h

@@ -828,6 +828,19 @@ static inline void netif_napi_add(struct net_device *dev,
 	set_bit(NAPI_STATE_SCHED, &napi->state);
 }
 
+/**
+ *  netif_napi_del - remove a napi context
+ *  @napi: napi context
+ *
+ *  netif_napi_del() removes a napi context from the network device napi list
+ */
+static inline void netif_napi_del(struct napi_struct *napi)
+{
+#ifdef CONFIG_NETPOLL
+	list_del(&napi->dev_list);
+#endif
+}
+
 struct packet_type {
 	__be16			type;	/* This is really htons(ether_type). */
 	struct net_device	*dev;	/* NULL is wildcarded here	     */