drm/msm/dpu: drop SSPP's SRC subblock

drm/msm/dpu: drop SSPP's SRC subblock

The src_blk declares a lame copy of main SSPP register space. It's
offset is always 0. It's length has been fixed to 0x150, while SSPP's
length is now correct. Drop the src_blk and access SSPP registers
without additional subblock lookup.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/534745/
Link: https://lore.kernel.org/r/20230429012353.2569481-2-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>