tcp: Fix error code check in syncache_respond()
tcp: Fix error code check in syncache_respond()

ofp_ip_output() return ofp-return_code enum but
syncache_respond() assummed an int (0 for success).
That led to intepreting ofp_ip_output result of OFP_PKT_PROCESSED (1)
as error and, in consequence, spurious dropping of syncache entry.

Signed-off-by: Maciej Czekaj <8d42daaa8d68ad54ca06613337e5c27633935527@caviumnetworks.com>
Reviewed-by: Sorin Vultureanu <8013ba55f8675034bc2ab0d6c3a1c9650437ca36@enea.com>

OpenFastPath/ofp,OpenFastPath/ofp,TolikH/ofp,OpenFastPath/ofp,OpenFastPath/ofp,TolikH/ofp,TolikH/ofp