drm/i915: Skip cursor when writing PLANE_CHICKEN

Cursor is not a universal plane and thus doesn't have the
PLANE_CHICKEN register. Skip it.

Fixes: c5de2484 ("drm/i915/dpt: Add a modparam to disable DPT via the chicken bit")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230329190445.13456-1-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>