Add support for Freescale Layerscape PCIe controller.  This driver re-uses
the Synopsis DesignWare core code.

[bhelgaas: add Kconfig dependency on CONFIG_ARM]
Signed-off-by: NMinghuan Lian <Minghuan.Lian@freescale.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>