drm/msm/dpu: Add support for MSM8996

Add support for MSM8996, which - fun fact - was the SoC that this driver
(or rather SDE, its downstream origin) was meant for and first tested on.

It has some hardware that differs from the modern SoCs, so not a lot of
current structs could have been reused. It's also seemingly the only SoC
supported by DPU that uses RGB pipes.

Note, by default this platform is still handled by the MDP5 driver
unless the `msm.prefer_mdp5=false' parameter is provided.

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
[DB: rebased on top of sblk changes, add dpu_rgb_sblk]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Konrad Dybcio <konrad.dybcio@linaro.org>
[Removed intr_start from CTLs config, removed LM_3 and LM_4]
Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/617309/
Link: https://lore.kernel.org/r/20240930-dpu-msm8953-msm8996-v2-1-594c3e3190b4@mainlining.org