drm/i915/display: Copy color pipeline from plane in the primary joiner pipe

drm/i915/display: Copy color pipeline from plane in the primary joiner pipe

When copying plane color state in a joiner configuration, use the plane in
the primary joiner pipe since it carries the pipeline number selected by
the user-space.

This assumes that all pipes in the joiner are symmetric in their plane
color capabilities.

Cc: stable@vger.kernel.org # v6.19+
Fixes: a78f1b6baf4d ("drm/i915/color: Add framework to program CSC")
Tested-by: Vidya Srinivas <vidya.srinivas@intel.com>
Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patch.msgid.link/20260511053213.3122314-2-chaitanya.kumar.borah@intel.com
(cherry picked from commit e8308fb5e05ca08ddfb8b46f6d947a6e3fd80cd7)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>