cxgbe/t4_tom: Track all synq entries in a per-adapter list.

Live tid entries in tid_tab are either full fledged connections or synq
entries. toep_list tracks the connections already and this change adds
a synqe_list to track the synq entries. These two lists can be used to
enumerate and iterate over all live tids.

MFC after: 1 week
Sponsored by: Chelsio Communications