q35 already has an 'audio0' device, rename our to "audiodev$id"

q35 already has an 'audio0' device, rename our to "audiodev$id"

The latest changes to our audio device implemenation [0] changed the
naming of the device id to "audio<id>" which in practice resulted in
"audio0".

This conflicts with the predefined audio device in the Q35 configs
that is also using "audio0". The result is that a VM with a
configured audio device and Q35 type will not start.

While we just would had removed the audio0 device if we had detected
this earlier in the new 4.0 q35 config, we cannot do so anymore due
to migration compatibility.

So rename the device from "audio$id" to audiodev$id".

Co-authored-by: Aaron Lauterer <a.lauterer@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>