drm/msm/dpu: add support for MDP_TOP blackhole

On sm8450 a register block was removed from MDP TOP. Accessing it during
snapshotting results in NoC errors / immediate reboot. Skip accessing
these registers during snapshot.

Tested-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/514239/
Link: https://lore.kernel.org/r/20221207012231.112059-10-dmitry.baryshkov@linaro.org


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