pseries: Fix qdev.id handling in the VIO bus code

pseries: Fix qdev.id handling in the VIO bus code

When the user creates a device on the command line with -device, they
can specify the id, using id=foo. Currently the VIO bus code overwrites
this id with it's own value. We should only set qdev.id if it is not
already set by the user.

The device tree code uses qdev.id for the device tree node name, however
we can't rely on the user specifiying the id using proper device tree
syntax, ie. device@reg. So separate the device tree node name from the
qdev.id, but use the same syntax, so they will match by default.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>