PCI: Fix enabling of PASID on RC integrated endpoints

Set the eetlp_prefix_path on PCIE_EXP_TYPE_RC_END devices to allow PASID
to be enabled on them.  This fixes IOMMUv2 initialization on AMD Carrizo
APUs.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=201079


Fixes: 7ce3f912 ("PCI: Enable PASID only if entire path supports End-End TLP prefixes")
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>