arm64: dts: qcom: sm6115: Use the correct DSI compatible

Use the non-deprecated, SoC-specific DSI compatible.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230307-topic-dsi_qcm-v6-9-70e13b1214fa@linaro.org