StarFive VisionFive 2 support

Hi,

I've been looking at support for the StarFive VisionFive 2 off and on for the last few weeks, using the OpenBSD support as a reference. Recently it was recommended to me that I check here whether anyone else was working on this before I got too far, to avoid duplicating and work.

The core of the support is the JH7110, which is also what's used in Pine64's Star64 and PineTab-V. I got the micro SD and eMMC working today with a temporary hack (I hard-coded a frequency because the clock-related potions of the DTBs for this board omit things FreeBSD expects; updating that code is next) and a local fix to build mmcsd as a module (I reported https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=274388).

Is anyone else working on support for any of these JH7110 devices? I'm having fun and happy to keep chugging along on my own, but if anyone else is already working on this perhaps I can focus on support for distinct parts of JH7110 support.

-Colin