New `graphics/drm-latest-kmod` port to track the latest version of the DRM drivers

Hi!

For those who wants to test and use the latest version of the DRM 
drivers that was ported to FreeBSD, you can now use the new 
graphics/drm-latest-kmod port. It is available as a binary package as well.

This port is meant to track the `master` branch of our drm-kmod 
repository [1]. This branch receives the updates of the DRM drivers from 
Linux, even non-LTS versions. As of this writing the latest version in 
this branch is Linux 6.9. The next one will be 6.10 [2]. The next LTS 
one will be 6.12 and it will have its own port (graphics/drm-612-kmod) 
when the time comes.

In general, the port will support the -CURRENT version of FreeBSD, as 
well as the latest release if if has the required kernel patches 
already. For instance, the current port supports FreeBSD 15.0. However, 
the next one, 6.10, will only work on -CURRENT until the kernel patches 
are merged into stable/15.

You can install these drivers like you do with drm-{61,66}-kmod:

     sudo pkg install drm-latest-kmod

… or build the port yourself.

Note that these drivers may be less stable than the LTS-based ones from 
Linux 6.1 and 6.6. If you hit a problem, please report it on GitHub [1].

This is part of the sponsored Laptop and Desktop Usability Improvements 
project [3] of the FreeBSD Foundation! Thank you :-)

[1] https://github.com/freebsd/drm-kmod
[2] https://github.com/freebsd/drm-kmod/pull/371
[3] 
https://freebsdfoundation.org/blog/why-laptop-support-why-now-freebsds-strategic-move-toward-broader-adoption/

-- 
Jean-Sébastien Pédron
The FreeBSD Project