arm64: dts: qcom: sm8550: add missing cpu-cfg interconnect path in the mdss node

arm64: dts: qcom: sm8550: add missing cpu-cfg interconnect path in the mdss node

The bindings requires the mdp0-mem and the cpu-cfg interconnect path,
add the missing cpu-cfg path to fix the dtbs check error and also to ensure
that MDSS has enough bandwidth to let HLOS write config registers.

Fixes: b8591df49cde ("arm64: dts: qcom: sm8550: correct MDSS interconnects")
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250227-topic-sm8x50-mdss-interconnect-bindings-fix-v5-1-bf6233c6ebe5@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>