dt-bindings: net: qcom: ethernet: Allow dma-coherent

On SA8775P, Ethernet DMA controller is coherent with the CPU.
allow specifying that.

Signed-off-by: Sagar Cheluvegowda <quic_scheluve@quicinc.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240514-mark_ethernet_devices_dma_coherent-v4-2-04e1198858c5@quicinc.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>