ctld: Always declare MaxRecvDataSegmentLength.

This key is Declarative and should always be sent even if the
initiator did not send it's own limit. This is similar to the fix in
fc79cf4fea72 but for the target side. However, unlike that fix,
failure to send the key simply results in reduced performance.

PR: 259439
Reviewed by: mav, emaste
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D32651