cfattach front-end code:
dc_ds for the decstation 2100( pmin), 3100 (pmax), and 5100.
dc_ioasic for the decstation 5000/200 (3max) which does not have a
DEC TC-style IOCTL asic, but is configured as if it did.
* Add pre-autoconfig code initialization of kerenl dc driver console I/O
for remote serial consoles. The hack to use PROM serial I/O until the
dc device is autoconfigured is no longer necessary.
