dt-bindings: dma: ti: Add document for K3 UDMA

dt-bindings: dma: ti: Add document for K3 UDMA

New binding document for
Texas Instruments K3 NAVSS Unified DMA – Peripheral Root Complex (UDMA-P).

UDMA-P is introduced as part of the K3 architecture and can be found in
AM654 and j721e.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Tested-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Link: https://lore.kernel.org/r/20191223110458.30766-10-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>