dt-bindings: dma: fsl,imx-dma: Document the DMA clocks

Document the IPG and AHB clocks that are needed by the DMA hardware
as required properties.

It is not possible to have DMA functional without the DMA clocks
being turned on.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240807170517.64290-1-festevam@gmail.com


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