pseries: Emit device tree nodes in reg order

pseries: Emit device tree nodes in reg order

Although in theory the device tree has no inherent ordering, in practice
the order of nodes in the device tree does effect the order that devices
are detected by software.

Currently the ordering is determined by the order the devices appear on
the QEMU command line. Although that does give the user control over the
ordering, it is fragile, especially when the user does not generate the
command line manually - eg. when using libvirt etc.

So order the device tree based on the reg value, ie. the address of on
the VIO bus of the devices. This gives us a sane and stable ordering.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
[agraf] add braces