dt-bindings: dma: qcom,gpi: Document the sm8750 GPI DMA engine

Document the GPI DMA engine on the sm8750 platform.

Signed-off-by: Melody Olvera <quic_molvera@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20241021230500.2632527-1-quic_molvera@quicinc.com


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