a band-aid allowing to call this function savely multiple times, e.g.
during sckbdprobe() and sc_probe_unit(). Otherwise calling it a second
time results in a non-working keyboard. This needs a lot of more work
to actually do the right thing and work like expected.
- Let sunkbd_configure() return the number of the found keyboards, i.e.
1 in case probing succeeds, as it's expected. The return values of the
keyboard configure functions however currently aren't checked so this
doesn't make a difference at the moment.
- Use FBSDID.
The presence or absence of a keyboard does not change whether an
UART is designed as a keyboard port or not and thus whether we
can use the port as a TTY or not.
We now call sunkbd_attach() even when we didn't previously find
a keyboard. Emit a useful message stating that no keyboard was
found, but don't do anything else.
MFC after: 5 days
