that a unit select did not complete and needs to be retried. Selection will
be retried following a disconnection if this flag is set. The function
sfas_select_unit() will set/clear this flag depending on when a selection
completed or not.
- split softc size and match/attach out from cfdriver into
a new struct cfattach.
- new "attach" directive for files.*. May specify the name of
the cfattach structure, so that devices may be easily attached
to parents with different autoconfiguration semantics.