drm/i915: Move skl+ wm/ddb registers to proper headers
On SKL+ the watermark/DDB registers are proper per-plane
registers. Move the definitons to their respective files.
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
CC: Zhi Wang <zhi.wang.linux@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240510152329.24098-5-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>