SB: Fix Windows 9x support (unimplemented DSP read and write status port bits should be pulled high)

[ianhan]

This change fixes Windows 9x driver support for SB mode by implementing a quirk the driver expects (unimplemented status bits should be pulled high). PCem does the same thing.

Tested with DXDiag and some audio playback apps. Tested with Jazz Jackrabbit and Cubic Player outside of Windows under DOS.