Documentation: devicetree: dma: update the comments

remove the double word to.

Signed-off-by: Deming Wang <wangdeming@inspur.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://lore.kernel.org/r/20220920020721.2190-1-wangdeming@inspur.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>