dts: bindings: dma: intel_lpss: Added phandle dma-parent

Added a phandle named dma-parent to get base address instead of
adding DMA as child node because it is causing a build warning
(avoid_unnecessary_addr_size) if the parent instance has
"#address-cells/#size-cells" dts properties marked required
and child doesn't have reg property. DMA doesn't have reg
as it gets the base address from parent device

Signed-off-by: Anisetti Avinash Krishna <anisetti.avinash.krishna@intel.com>