Add the sabtty children devices as unordered.  Use the unit numbr of the sabtty device to create its description so that they will be unique for machines with multiple sab chips.
Add the sabtty children devices as unordered.  Use the unit numbr of
the sabtty device to create its description so that they will be
unique for machines with multiple sab chips.

This fixes a panic on machines with an rsc card.

Tested by:	obrien (e250)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase