PCI: dwc: Add debugfs support for PTM context

Synopsys Designware PCIe IPs support PTM capability as defined in the PCIe
spec r6.0, sec 6.21. The PTM context information is exposed through Vendor
Specific Extended Capability (VSEC) registers on supported controller
implementation.

Hence, add support for exposing these context information to userspace
through the debugfs interface for the DWC controllers (both RC and EP).
Currently, only Qcom controllers are supported. For adding support for
other DWC vendor controllers, dwc_pcie_ptm_vsec_ids[] needs to be extended.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Link: https://patch.msgid.link/20250505-pcie-ptm-v4-3-02d26d51400b@linaro.org