Use the for_each_of_cpu_node iterator to iterate over cpu nodes. This
has the side effect of defaulting to iterating using "cpu" node names in
preference to the deprecated (for FDT) device_type == "cpu".
This also fixes a leaked reference for cpus node.
Cc: Jonas Bonn <jonas@southpole.se> Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi> Cc: openrisc@lists.librecores.org Acked-by: Stafford Horne <shorne@gmail.com> Signed-off-by: Rob Herring <robh@kernel.org>