drm/msm/dpu: fix DSC 1.2 enc subblock length

Both struct dpu_dsc_sub_blks instances declare enc subblock length to be
0x100, while the actual length is 0x9c (last register having offset 0x98).
Reduce subblock length to remove the empty register space from being
dumped.

Fixes: 0d1b10c6 ("drm/msm/dpu: add DSC 1.2 hw blocks for relevant chipsets")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/550999/
Link: https://lore.kernel.org/r/20230802183655.4188640-2-dmitry.baryshkov@linaro.org