tcpsso: fix when used without -i option

Since fdb987bebddf it is not possible anymore to use inp_next
iterator for bound, but unconnected sockets. This applies
to TCP listening sockets. Therefore the metioned commit broke
tcpsso on listening sockets if the -i option was not used.
Fix this by iterating through all endpoints instead of only
through the bound, but unconnected ones.

Reviewed by: markj
Fixes: fdb987bebddf ("inpcb: Split PCB hash tables")
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D43353

(cherry picked from commit 13720136fbf951a7b472ce086c9cf2de702799ab)