tree... John Baldwin noted that sio might pass values between probe
and attach via softc. It appears that sio does leave the hardware in
a known state after probing, so other drivers that try to probe might
leave it in a worse state. It doesn't seem to pass any data in softc,
however, that I could find... I think we should not be probing for
anything but nonPnP isa, but that's a change for another day.
Submitted by: Frank Behrens
PR: 87845