dmaengine: mmp: deprecate '#dma-channels'

The generic property, used in most of the drivers and defined in generic
dma-common DT bindings, is 'dma-channels'.  Switch to new property while
keeping backward compatibility.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220503065407.52188-4-krzysztof.kozlowski@linaro.org


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