USB and PCI soundcards have a nice set of ID_* properties. It would
be handy for firewire soundcards to have the same.
Note that this removes the explicit setting of ID_ID in the firewire
conditional. Because we are now setting ID_SERIAL, ID_ID will come
from later in the file.
The ALSA id sysattr is generated by the sound subsystem and is not
a stable identifier. It is generated though some string manipulation
then made unique if there is a conflict. This means that it is
enumeration-dependent and shouldn't be used for ID_ID.
If ID_ID is supposed to be system-unique, it is not already since
for firewire it is generated from the guid and there are broken
firewire devices that have duplicate guids across devices.
This is tracked for PulseAudio at
https://bugs.freedesktop.org/show_bug.cgi?id=90129.
This is essentially a revert of systemd
ed1b2d9fc7.
