dts: renesas: smartbond: Add missing #dma-cells binding

This commit should address the #73803 issue
where the DMA node does not provide support
for the #dma-cells binding. Peripherals should
specify one or more DMA channels via the dmas
and optionally dma-names DT properties.

Signed-off-by: Ioannis Karachalios <ioannis.karachalios.px@renesas.com>