arm64: dts: ls1028a: add "fsl,vf610-edma" compatible

The bootloader does the IOMMU fixup and dynamically adds the "iommus"
property to devices according to its compatible string. In case of the
eDMA controller this property is missing. Add it. After that the IOMMU
will work with the eDMA core.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>