drm/i915/overlay: Extract i915_overlay_is_active()
Pull the "is the overlay active?" check to a helper
(i915_overlay_is_active()). This will have to move to the
i915 side of the parent vs. display driver split.
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260226100738.29997-4-ville.syrjala@linux.intel.com