linux-phytec-ti

dt-bindings: PCI: Add dt binding for setting PCI mode in pci-keystone

Document "ti,syscon-dev" property that should be used to set the
PCIe mode in pci-keystone driver.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>