drm/msm/dpu: Add DSPP GC driver to provide GAMMA_LUT DRM property

drm/msm/dpu: Add DSPP GC driver to provide GAMMA_LUT DRM property

Add support for DSPP GC block in DPU driver for Qualcomm SoCs.
Expose the GAMMA_LUT DRM property, which is needed to enable
night light and basic screen color calibration.

I used LineageOS downstream kernel as a reference and found the LUT
format by trial-and-error on OnePlus 6.

Tested on oneplus-enchilada (sdm845-mainline 6.16-dev) and xiaomi-tissot
(msm8953-mainline 6.12/main).

Tested-by: David Heidelberg <david@ixit.cz>  # Pixel 3 (next-20251018)
Tested-by: Guido Günther <agx@sigxcpu.org> # on sdm845-shift-axolotl
Signed-off-by: Federico Amedeo Izzo <federico@izzo.pro>
Tested-by: Steev Klimaszewski <threeway@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/682102/
Link: https://lore.kernel.org/r/20251019-dpu-add-dspp-gc-driver-v3-1-840491934e56@izzo.pro
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>