explicit NewReno module dependency

[rscheff]

Summary

Add explicit NewReno module dependency to all modular congestion control methods

The default and fall-back congestion control mechanism is always NewReno. In
order to prevent someone mistakenly trying to not load newreno, add an explicit
module dependency.

To keep things simple, added FreeBSD major version as the reference.

Typically, the TCP code is fairly stable though.

[tuexen]

I think this is not needed, since cc_newreno is statically compiled into the kernel and not compiled as a module.