dt-bindings: PCI: Remove 83xx-512x-pci.txt

This binding is already covered by fsl,mpc8xxx-pci.yaml schema. While
the MPC512x is mentioned here, its compatible strings aren't actually
documented and remain that way.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250710180843.2971667-1-robh@kernel.org

Author: robherring