spapr.c: add 'name' property for hotplugged CPUs nodes

spapr.c: add 'name' property for hotplugged CPUs nodes

In the CPU hotunplug bug [1] the guest kernel throws a scary
message in dmesg:

pseries-hotplug-cpu: Failed to offline CPU <NULL>, rc: -16

The reason isn't related to the bug though. This happens because the
kernel file arch/powerpc/platform/pseries/hotplug-cpu.c, function
dlpar_cpu_remove(), is not finding the device_node.name of the offending
CPU.

We're not populating the 'name' property for hotplugged CPUs. Since the
kernel relies on device_node.name for identifying CPU nodes, and the
CPUs that are coldplugged has the 'name' property filled by SLOF, this
is creating an unneeded inconsistency between hotplug and coldplug CPUs
in the kernel.

Let's fill the 'name' property for hotplugged CPUs as well. This will
make the guest dmesg throws a less intimidating message when we try to
unplug the last online CPU:

pseries-hotplug-cpu: Failed to offline CPU PowerPC,POWER9@1, rc: -16

[1] https://bugzilla.redhat.com/1911414

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210120232305.241521-3-danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>