Summary

1. Allow agpMoveCMD register reads.
2. Fix bad depth + 16-bit RGB565 writes.

Checklist

• Closes 86Box crashed when I use voodoo 3000 to run "Wing Command - Prophecy" in Windows 2000 Professional. #6461
• I have tested my changes locally and validated that the functionality works as intended
• I have discussed this with core contributors already
• This pull request requires changes to the ROM set
  • I have opened a roms pull request - https://github.com/86Box/roms/pull/changeme/
• This pull request requires changes to the asset set
  • I have opened an assets pull request - https://github.com/86Box/assets/pull/changeme/

References

None.