- Change the attimer <-> pcppi communication using device_t so that
pcppi(4) doesn't have to know about the contents of struct attimer_softc.
XXX pcppi's childdet function is completely wrong. This has to be
XXX revisited later.
attimer(4) is the new body of the part of pcppi(4) that mapped the TIMER1
register to set the pitch of the bell. It was necessary to separate them
in order to have a working ACPI attachment (as the two appear as different
devices in the ACPI structures).