[NET]: docbook fixes for netif_ functions

Documentation updates for network interfaces.

1. Add doc for netif_napi_add
2. Remove doc for unused returns from netif_rx
3. Add doc for netif_receive_skb

[ Incorporated minor mods from Randy Dunlap -DaveM ]

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9b0c8f1..1e6af4f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -739,6 +739,16 @@
  */
 #define SET_NETDEV_DEV(net, pdev)	((net)->dev.parent = (pdev))
 
+/**
+ *	netif_napi_add - initialize a napi context
+ *	@dev:  network device
+ *	@napi: napi context
+ *	@poll: polling function
+ *	@weight: default weight
+ *
+ * netif_napi_add() must be used to initialize a napi context prior to calling
+ * *any* of the other napi related functions.
+ */
 static inline void netif_napi_add(struct net_device *dev,
 				  struct napi_struct *napi,
 				  int (*poll)(struct napi_struct *, int),