multimedia/libdv: Re-enable tools (partially)

[diizzy]

Summary

Re-enable utilities that is used for encoding and stream processing
Thankfully upstream haven't connected playdv so no additional dependencies are needed.

Fixes https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=259695

Test Plan

Compile tested on FreeBSD 13.0-STABLE #1 stable/13-n247667-dc9094140c9 (amd64) (make, make check-plist)
Poudriere testport OK 12.2-RELEASE (amd64)
Poudriere testport OK 13.0-RELEASE (i386)

[tcberner]

This looks like something that you can do with implicit approval to me.