drm/i915/mst: Reject FEC+MST on ICL

ICL supposedly doesn't support FEC on MST. Reject it.

Cc: stable@vger.kernel.org
Fixes: d51f25eb ("drm/i915: Add DSC support to MST path")
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240402135148.23011-7-ville.syrjala@linux.intel.com


(cherry picked from commit b648ce2a)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>