PCI: dwc: pci-dra7xx: Fix a leaked reference by adding missing of_node_put()

PCI: dwc: pci-dra7xx: Fix a leaked reference by adding missing of_node_put()

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

irq_domain_add_linear() also calls of_node_get() to increase refcount,
so irq_domain will not be affected when it is released.

Detected by coccinelle with the following warnings:

  ./drivers/pci/controller/dwc/pci-dra7xx.c:252:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 241, but without a corresponding object release within this function.
  ./drivers/pci/controller/dwc/pci-dra7xx.c:255:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 241, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-omap@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: linux-kernel@vger.kernel.org