arm64: dts: qcom: sc7280: Don't disable MDP explicitly

MDSS and all its subdevices are useless without DPU/MDP, so disabling
MDP doesn't make any sense. Remove explicit disabling of the DPU device.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230531011623.3808538-2-dmitry.baryshkov@linaro.org