Remove the atkbd, psm, sc and vga devices. Most ia64 boxes out there

Remove the atkbd, psm, sc and vga devices. Most ia64 boxes out there
are zx1 based machines and they don't particularly like it when we
poke at them with PC legacy code. The atkbd and psm devices were
disabled in the hints file so that one could enable them on machines
that support legacy devices, but that's not really something you can
expect from a first-time installer. This still leaves syscons (sc)
and the vga device, which were enabled by default and wrecking havoc
anyway. We could disable them by default like the atkbd and psm
devices, but there's really no point in pretending we're in a better
shape that way.