PCI: dwc: ep: Introduce dw_pcie_ep_cleanup() API for drivers supporting PERST#

For DWC glue drivers supporting PERST# (currently Qcom and Tegra194), some
of the DWC resources like eDMA should be cleaned up during the PERST#
assert time.

So let's introduce a dw_pcie_ep_cleanup() API that could be called by these
drivers to cleanup the DWC specific resources. Currently, it just removes
eDMA.

Closes: https://lore.kernel.org/linux-pci/ZWYmX8Y%2F7Q9WMxES@x1-carbon
Link: https://lore.kernel.org/linux-pci/20240327-pci-dbi-rework-v12-5-082625472414@linaro.org


Reported-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Niklas Cassel <cassel@kernel.org>