avf: Fix cksum offload / ipsec
avf: Fix cksum offload / ipsec

VNET_BUFFER_F_OFFLOAD means 'check 2nd cacheline'
but we can still have TCP_CKSUM=0 & UDP_CKSUM=0

Type: fix

Change-Id: I42b5974f6d34b777aa959c06c67619a5c83c5805
Signed-off-by: Nathan Skrzypczak <0fa918c439baf617eab84c5ae2a48ee9db643966@gmail.com>

chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp