test: if the user enters DMA channel configuration for non-PnP SB16 that
is impossible, then match what the hardware will do: Either allow DMA16
to 5,6,7 or match the 8-bit DMA channel. Add more code to the core
library to NOT autoprobe if it knows how to read configuration from a
non-PnP SB16.
added code where if SC-6000 clone is detected, it will read
configuration from it, then set the necessary flags to not probe IRQ and
DMA configuration later. Also forgot to mention in previous commit that
code was added to the PnP support function to consider special values in
PnP specification that mean "unassigned" rather than blindly taking the
byte values.