PCI: xgene: Drop XGENE_PCIE_IP_VER_UNKN

PCI: xgene: Drop XGENE_PCIE_IP_VER_UNKN

XGENE_PCIE_IP_VER_UNKN is only refered to when probing for the
original XGene PCIe implementation, and get immediately overridden
if the device has the "apm,xgene-pcie" compatible string.

Given that the only way to get there is by finding this very string in
the DT, it is obvious that we will always overwrite the version with
XGENE_PCIE_IP_VER_1.

Drop the whole thing.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20250708173404.1278635-5-maz@kernel.org