change drive state to emulate BIOS carrying out a disk reset function.
IDE emulation: add disk reset INT 13h emulation. added code to set
status to DISK_READY|SEEK_COMPLETE upon completing common functions.
This succeeds in getting past some initial checks in WDCTRL in WfW 3.11
so far. Now all we need is for INT 13h "read disk" code to change IDE
registers as well because WDCTRL "tests" for validity by executing INT
13h then reading back IDE registers.