Floppy and hard disk fixes for IBM PS/2 model 30-286

[WNT50]

Summary

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

• Pull down keyboard input port pin 6 to allow PS/2 model 30-286 rev. 0 BIOS to recognize drive A as 1.44M floppy
• WRITE VERIFY command in IBM PS/1 XTA disk controller should write data to disk (unlike READ VERIFY command), fixes NetWare 2.2 ZTEST and COMPSURF failing to verify disk for bad sectors

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

IBM PS/2 model 30-286 schematics: https://www.ardent-tool.com/docs/pdf/schematics/m30-286_sch.pdf