PCI: dwc: Expose PCIe event counters for groups 5 to 7 over debugfs

PCI: dwc: Expose PCIe event counters for groups 5 to 7 over debugfs

Extend the DesignWare PCIe controller's debugfs statistical counter
interface with event definitions from groups 5 through 7 as documented
in the DWC PCIe Databook (version 6.30a, section 3.8.2.3, Tables 3-59,
3-60, 3-61). These counters provide visibility into Layer1 non-error
events (link state transitions,ASPM, L1 substates), Layer2 DLLP
exchanges, and Layer3 TLP transactions.

The counters are exposed under the debugfs statistical counter directory,
allowing users to monitor link behavior and diagnose PCIe protocol issues
more effectively.

Co-developed-by: Cheng Xin <chengqin195275@126.com>
Signed-off-by: Cheng Xin <chengqin195275@126.com>
Signed-off-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Link: https://patch.msgid.link/20260307020152.1224518-1-18255117159@163.com