Merge branch 'eth_get_headlen'

Alexander Duyck says:

====================
net: Drop get_headlen functions in favor of generic function

This series replaces the igb_get_headlen and ixgbe_get_headlen functions
with a generic function named eth_get_headlen.

I have done some performance testing on ixgbe with 258 byte frames since
the calls are only used on frames larger than 256 bytes and have seen no
significant difference in CPU utilization.

v2: renamed __skb_get_poff to skb_get_poff
    renamed ___skb_get_poff to __skb_get_poff
====================

Signed-off-by: David S. Miller <davem@davemloft.net>