o Remove ttyyX, created by the obsolete zs(4)
o Replace ttydX by ttyuX, which is created by uart(4)
o Enable ttyu0 as a console to better support the xserve.
MFC after: 1 week
The OpenFirmware console isn't used on real systems anymore and
I never get to multi-user mode in psim. There are problems with
zs that need to be resolved before these lines can be enabled.
This eliminates disconcerting warnings on boot.
MFC after: 2 days
