cxgbe/t4_tom: Handle VXLAN-encapsulated SYNs correctly.

TCP SYNs in inner traffic will hit hardware listeners when VXLAN/NVGRE
rx parsing is enabled in the chip. t4_tom should pass on these SYNs to
the kernel and let it deal with them as if they arrived on the non-TOE
path.

Reported by: Sony at Chelsio
MFC after: 1 week
Sponsored by: Chelsio Communications