pci: layerscape: add pci driver based on DM

pci: layerscape: add pci driver based on DM

There are more than five kinds of Layerscape SoCs. unfortunately,
PCIe controller of each SoC is a little bit different. In order
to avoid too many macro definitions, the patch addes a new
implementation of PCIe driver based on DM. PCIe dts node is
used to describe the difference.

Signed-off-by: Minghuan Lian <[email protected]>
Signed-off-by: Hou Zhiqiang <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: York Sun <[email protected]>