net: move *skb_get_poff declarations into correct header

Since these functions are defined in flow_dissector.c, move header
declarations from skbuff.h into flow_dissector.h

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/linux/skbuff.h
Simple merge

diff --cc include/net/flow_dissector.h
Simple merge

diff --cc net/core/filter.c
Simple merge

diff --cc net/ethernet/eth.c
Simple merge