arm64: dts: layerscape: add iommu-map property to pci nodes

Add the iommu-map property to the pci nodes so that the firmware
fixes it up with the required values thus enabling iommu for
devices connected over pci.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>