ARM: dts: am33xx: use new 'dma-channels/requests' properties

The '#dma-channels' and '#dma-requests' properties were deprecated in
favor of these defined by generic dma-common DT bindings.  Add new
properties while keeping old ones for backwards compatibility.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Message-Id: <20220503065201.51818-5-krzysztof.kozlowski@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>