PCI: qcom: Remove DPC Extended Capability

PCI: qcom: Remove DPC Extended Capability

Some platforms (e.g., X1E80100) expose Downstream Port Containment (DPC)
Extended Capability registers in the PCIe Root Port config space, but do
not fully support it. To prevent undefined behavior and ensure DPC cap is
not visible to PCI framework and users, remove DPC Extended Capability
unconditionally, since there is no Qcom platform support DPC till now.

Co-developed-by: Wenbin Yao <wenbin.yao@oss.qualcomm.com>
Signed-off-by: Wenbin Yao <wenbin.yao@oss.qualcomm.com>
Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20251109-remove_cap-v1-5-2208f46f4dc2@oss.qualcomm.com