Hardware: disk seek time intended to be per-track

[branlwyd]

Disk seek time is intended to be per-track. However it's currently either 0 (if the requested data is on the same track) or the seek time of a single track (if the data isn't on the same track).

The seek time should be proportional to the number of tracks between the last read and the current one.

Per the specification:

Track seeking time is about 2.4 ms per track.

[branlwyd]

This fix was included among the general hardware scheduled-wait refactoring in e204532.