nfp: tls: use unique connection ids instead of 4-tuple for TX

Connection 4 tuple reuse is slightly problematic - TLS socket
and context do not get destroyed until all the associated skbs
left the system and all references are released. This leads
to stale connection entry in the device preventing addition
of new one if the 4 tuple is reused quickly enough.

Instead of using read 4 tuple as the key use a unique ID.
Set the protocol to TCP and port to 0 to ensure no collisions
with real connections.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>