perf/dwc_pcie: Move common DWC struct definitions to 'pcie-dwc.h'

Move the common DWC struct definitions, which are shared across all the
DesginWare PCIe IPs, to a new header file called 'pcie-dwc.h', so that
other users e.g., debugfs, perf and sysfs can make use of them.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Shradha Todi <shradha.t@samsung.com>
Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Tested-by: Hrishikesh Deleep <hrishikesh.d@samsung.com>
Link: https://lore.kernel.org/r/20250221131548.59616-2-shradha.t@samsung.com


[kwilczynski: commit log, tidy up the new header file]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>