dt-bindings: dma: ti: k3-udma: Update for atype support (virtualization)

dt-bindings: dma: ti: k3-udma: Update for atype support (virtualization)

In UDMA each channel can use different ATYPE value which tells UDMA how
the addresses in the descriptors should be treated:
0: pointers are physical addresses (no translation)
1: pointers are intermediate addresses (PVU)
2: pointers are virtual addresses (SMMU)

When virtualized environment is used then the dma binding should use
additional cell to configure the desired ATYPE for the channel.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200218143126.11361-2-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>