Summary

1. This fixes wrong refresh rates of the Oak VGA chips.
2. VGA mode bit 7 (oak reg 0x0e) when in text mode should clear the banking if so desired (assuming VGA mode means non-extended modes) (this fixes garbled command prompts, but report any regressions please if any).

Checklist

• Closes #xxx
• 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

OAK OTI068 clock databook