cxgbe/t4_tom: fixes for issues on the passive open side.
- Fix PR 227760 by getting the TOE to respond to the SYN after the call
to toe_syncache_add, not during it. The kernel syncache code calls
syncache_respond just before syncache_insert. If the ACK to the
syncache_respond is processed in another thread it may run before the
syncache_insert and won't find the entry. Note that this affects only
t4_tom because it's the only driver trying to insert and expand
syncache entries from different threads.
- Do not leak resources if an embryonic connection terminates at
SYN_RCVD because of L2 lookup failures.
- Retire lctx->synq and associated code because there is never a need to
walk the list of embryonic connections associated with a listener.
The per-tid state is still called a synq entry in the driver even
though the synq itself is now gone.
PR: 227760
MFC after: 2 weeks
Sponsored by: Chelsio Communications
UnifiedSplitRaw
