dt-bindings: display/msm: merge SM8550 DPU into SC7280

dt-bindings: display/msm: merge SM8550 DPU into SC7280

Split of the bindings was artificial and not helping - we end up with
multiple binding files for very similar devices thus increasing the
chances of using different order of reg and clocks entries.

Unify DPU bindings of SC7280 and SM8550, because they are the same.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/617874/
Link: https://lore.kernel.org/r/20241003-dt-binding-display-msm-merge-v1-5-91ab08fc76a2@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>