PCI: keystone: Fix interrupt-controller-node lookup

commit eac56aa3bc8af3d9b9850345d0f2da9d83529134 upstream.

Fix child-node lookup during initialisation which was using the wrong
OF-helper and ended up searching the whole device tree depth-first
starting at the parent rather than just matching on its children.

To make things worse, the parent pci node could end up being prematurely
freed as of_find_node_by_name() drops a reference to its first argument.
Any matching child interrupt-controller node was also leaked.

Fixes: 0c4ffcfe ("PCI: keystone: Add TI Keystone PCIe driver")
Cc: stable <stable@vger.kernel.org>     # 3.18
Acked-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
[lorenzo.pieralisi@arm.com: updated commit subject]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[johan: backport to 4.4]
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>