dt-bindings: dma: xilinx: Add power-domains to xlnx,zynqmp-dpdma

DP DMA has own power domain that's why describe required power-domain
property.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/8f5651634df338743f95a7253a741f9ddc92487d.1683891609.git.michal.simek@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>