PCI: dwc: Introduce generic controller capabilities interface

Since in addition to the already available iATU unrolled mapping we are
about to add a few more DW PCIe platform-specific capabilities (CDM-check
and generic clocks/resets resources) let's add a generic interface to set
and get the flags indicating their availability. The new interface shall
improve maintainability of the platform-specific code.

Link: https://lore.kernel.org/r/20221113191301.5526-17-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>