[NET]: fix net-core kernel-doc

Warning(/var/linsrc/linux-2617-g4//include/linux/skbuff.h:304): No description found for parameter 'dma_cookie'
Warning(/var/linsrc/linux-2617-g4//include/net/sock.h:1274): No description found for parameter 'copied_early'
Warning(/var/linsrc/linux-2617-g4//net/core/dev.c:3309): No description found for parameter 'chan'
Warning(/var/linsrc/linux-2617-g4//net/core/dev.c:3309): No description found for parameter 'event'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a45bba9..16eef03 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -215,6 +215,8 @@
  *	@nf_bridge: Saved data about a bridged frame - see br_netfilter.c
  *	@tc_index: Traffic control index
  *	@tc_verd: traffic control verdict
+ *	@dma_cookie: a cookie to one of several possible DMA operations
+ *		done by skb DMA functions
  *	@secmark: security marking
  */