dt-bindings: dma: qcom,gpi: document the SDX75 GPI DMA Engine

Document the GPI DMA Engine on the SDX75 Platform.

Signed-off-by: Rohit Agarwal <quic_rohiagar@quicinc.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240517100423.2006022-2-quic_rohiagar@quicinc.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>