dt-bindings: dmaengine: xilinx_dma: Remove axidma multichannel support

The AXI DMA multichannel support is deprecated in the IP and it is no
longer actively supported. For multichannel support, refer to the AXI
multichannel direct memory access IP product guide(PG228) and MCDMA
driver(added in the subsequent commits). Inline with it remove axidma
multichannel optional properties i.e xlnx,mcdma and dma-channels from
the binding description.
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1571763622-29281-2-git-send-email-radhey.shyam.pandey@xilinx.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt

@@ -42,7 +42,6 @@ Optional properties for AXI DMA:
 	register as configured in h/w. Takes values {8...26}. If the property
 	is missing or invalid then the default value 23 is used. This is the
 	maximum value that is supported by all IP versions.
-- xlnx,mcdma: Tells whether configured for multi-channel mode in the hardware.
 Optional properties for VDMA:
 - xlnx,flush-fsync: Tells which channel to Flush on Frame sync.
 	It takes following values:
@@ -69,8 +68,6 @@ Optional child node properties for VDMA:
 	enabled/disabled in hardware.
 - xlnx,enable-vert-flip: Tells vertical flip is
 	enabled/disabled in hardware(S2MM path).
-Optional child node properties for AXI DMA:
--dma-channels: Number of dma channels in child node.
 
 Example:
 ++++++++