dt-bindings: display/msm: another fix for the dpu-qcm2290 example

Make dpu-qcm2290 example really follow the defined schema:
- Drop qcom,mdss compatible. It's only used for MDP5 devices.
- Change display controller name to display-controller as specified in
  the yaml

Reported-by: Rob Herring <robh@kernel.org>
Cc: Loic Poulain <loic.poulain@linaro.org>
Fixes: 164f69d9

 ("dt-bindings: msm: disp: add yaml schemas for QCM2290 DPU bindings")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20220324115536.2090818-1-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>