The code in camperiphunit rejects "scbus" as an 'at' location that would
allow any other wiring to use that unit number. Yet in
camperiphunitnext, if we have a no target and the 'at' location of
'scbus' it would be excluded on the basis that it's a wiring
cadidate. This is improper and appears to be a hold-over of the
pre-hints / pre-newbus config system, so remove it.
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