powerpc/powermac/feature: Add missing of_node_put()

In probe_one_macio(), call of_node_put() for the refernece 'node'
escaped out of the for_each_node_by_name() which has increased its
refcount. While the 'node' will finally escaped into a global reference,
we should still call of_node_put() in fail path which will stop global
reference creation.

Signed-off-by: Liang He <windhl@126.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220716065412.539153-1-windhl@126.com