It was added for netlink mmap tx, there are no callers in the tree.
The commit also added a check for skb->head != NULL in kfree_skb path,
remove that too -- all skbs ought to have skb->head set.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>