arm64: dts: exynos: drop useless 'dma-channels/requests' properties

The pl330 DMA controller provides number of DMA channels and requests
through its registers, so duplicating this information (with a chance of
mistakes) in DTS is pointless.  Additionally the DTS used always wrong
property names which causes DT schema check failures - the bindings
documented 'dma-channels' and 'dma-requests' properties without leading
hash sign.

Reported-by: Rob Herring <robh@kernel.org>
Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220430121902.59895-9-krzysztof.kozlowski@linaro.org