drm/msm/dpu: Update dev core dump to dump registers of sub-blocks

Currently, the device core dump mechanism does not dump registers of
sub-blocks within the DSPP, SSPP, DSC, and PINGPONG blocks. Edit
dpu_kms_mdp_snapshot function to account for sub-blocks.

Signed-off-by: Ryan McCann <quic_rmccann@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/546192/
Link: https://lore.kernel.org/r/20230622-devcoredump_patch-v5-6-67e8b66c4723@quicinc.com


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