The previous commit fixed -current on alpha for machines with

The previous commit fixed -current on alpha for machines with
serial console connections but not graphical consoles.  This fixes the
graphical console machines.  It leaves the initial promcons console
driver in place until a bit later in the boot sequence, delaying the
switch to the device drivers more appropriate for the machine's real
console setup.  Note we still need the delayed make_dev() for promcons,
it does not have a proper bus interface so unlike other console drivers
it will not be found later during normal device discovery.

Tested by:			sepotvin <at> videotron <dot> ca
Root cause explained by:	grehan (-current)
Approved by:			rwatson (mentor)