Summary

This PR makes the following changes to the IBM PS/2 model 30-286:

• Add rev. 0 BIOS for IBM PS/2 Model 30-286. Rev. 0 BIOS has hidden fonts which can be enabled by FONTMGR.SYS and FONTSEL.COM on the IBM PS/2 Model 30-286 starter disk, which doesn't work on the rev. 2 BIOS (33f5381a.bin) due to memory locations being moved.
• Fix starter disk always report 512KB of memory being installed (although normal operation is not affected). IBM PS/2 Model 30-286 uses two pins on the keyboard controller to report memory configuration based on the schematics, and this PR fixes the issue.

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 - Add IBM PS/2 Model 30-286 rev. 0 BIOS roms#460
• This pull request requires changes to the asset set
  • I have opened an assets pull request - https://github.com/86Box/assets/pull/changeme/

References

IBM PS/2 model 30-286 schematics: https://www.ardent-tool.com/docs/pdf/schematics/m30-286_sch.pdf
Fonts on IBM PS/2 Model 30-286 rev. 0 BIOS: https://int10h.org/blog/2022/06/ibm-ps2-30-286-hidden-vga-fonts/

Screenshots