uart(4) to support the Zilog 8530 SCCs which hang off of a FireHose
bus on Sun E4000/E5000 class machines.
Beside the fact that a puc_fhc.c would just be a copy of puc_sbus.c
with s,sbus,fhc,g the reason why the declaration for fhc(4) was
sticked into puc_sbus.c is that both of these front-ends for puc(4)
will go away once there is a scc(4).
Discussed with: marcel
Tested by: hrs, kris
MFC after: 3 days
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