[PATCH net] PCI: fix the return value for the pci_find_pcie_root_port()

From: Ding Tianhong <redacted>
Date: Thu, 17 Aug 2017 10:25:30 +0800

The pci_find_pcie_root_port() would return NULL if the given
dev is already a Root Port, it looks like unfriendly to the
PCIe Root Port device, Thierry and Bjorn suggest to let this
function return the given dev under this circumstances.

Fixes: 0e405232871d6 ("PCI: fix oops when try to find Root Port for a PCI device")
Suggested-by: Thierry Reding <redacted>
Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Thierry Reding <redacted>
Signed-off-by: Ding Tianhong <redacted>

Bjorn, please review and ACK so Linus doesn't rip my head off again
:-)

Thanks.