dt-bindings: display: msm: sm8450-mdss: Fix DSI compatible

The DSI compatible changed between patchset revisions, but that wasn't
reflected in the bindings. Fix it.

Fixes: 0eda3c6c ("dt-bindings: display/msm: add support for the display on SM8450")
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/528589/
Link: https://lore.kernel.org/r/20230323-topic-sm8450-upstream-dt-bindings-fixes-v2-1-0ca1bea1a843@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>