arm64: zynqmp: Get rid of iommus/power-domains properties for SPL DT

SPL DT contains only nodes which are contain u-boot,dm-pre-reloc property.
iommu node is not this case that's why when DT is read DTC reports some
warnings.

$ dtc -I dtb -O dts dts/dt-spl.dtb >/dev/null
<stdout>: Warning (iommus_property): /amba/spi@ff0f0000:iommus: Could not get phandle node for (cell 0)
<stdout>: Warning (iommus_property): /amba/mmc@ff160000:iommus: Could not get phandle node for (cell 0)
<stdout>: Warning (iommus_property): /amba/mmc@ff170000:iommus: Could not get phandle node for (cell 0)

SPL also has an option to remove some DT properties which are useless for
SPL to make DT even smaller.
Default DT properties are pinctrl-0 pinctrl-names interrupt-parent
interrupts which are already removed.
The patch extends this list with iommus to get rid of above warnings.
Also power-domains unused properties can be removed.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>