cxgbe/t4_tom: Free up hardware resources when the final CPL is received.

Final CPL means the tid is done in the hardware and other resources
associated with it can be freed right away. There is no need to wait
for the kernel to detach the toepcb.

Reviewed by: jhb
MFC after: 1 week
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D45991