Use tcpinfoh_t for TCP headers in the tcp:::debug-{drop,input} probes.

The header passed to these probes has some fields converted to host
order by tcp_fields_to_host(), so the tcpinfo_t translator doesn't do
what we want.

Submitted by: Hannes Mehnert
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D12647