of: Fix cpu node iterator to not ignore disabled cpu nodes

In most cases, nodes with 'status = "disabled";' are treated as if the
node is not present though it is a common bug to forget to check that.
However, cpu nodes are different in that "disabled" simply means offline
and the OS can bring the CPU core online. Commit f1f207e4 ("of: Add
cpu node iterator for_each_of_cpu_node()") followed the common behavior
of ignoring disabled cpu nodes. This breaks some powerpc systems (at
least NXP P50XX/e5500). Fix this by dropping the status check.

Fixes: 651d44f9 ("of: use for_each_of_cpu_node iterator")
Fixes: f1f207e4

 ("of: Add cpu node iterator for_each_of_cpu_node()")
Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>