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 <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <york.sun@nxp.com>