arm64: dts: qcom: sa8775p: Use a SoC-specific compatible for GPI DMA

arm64: dts: qcom: sa8775p: Use a SoC-specific compatible for GPI DMA

The commit adding these nodes did not use a SoC-specific node, fix that
to comply with bindings guidelines.

Fixes: 34d17ccb5db8 ("arm64: dts: qcom: sa8775p: Add GPI configuration")
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20241108-topic-sa8775_dma2-v1-2-1d3b0d08d153@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>