PCI: faraday: Add missing of_node_put()

The call to of_get_next_child() returns a node pointer with refcount
incremented thus it must be explicitly decremented here in the error
path and after the last usage.

Fixes: d3c68e0a ("PCI: faraday: Add Faraday Technology FTPCI100 PCI Host Bridge driver")
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>