arm64: dts: ls208xa: comply with the iommu map binding for fsl_mc

fsl-mc bus support the new iommu-map property. Comply to this binding
for fsl_mc bus.

Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>