drm/i915/fbc: Don't use a fence for a plane if FBC is not possible

No point in wasting a fence on a plane if it can't do FBC anyway.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240123090051.29818-1-ville.syrjala@linux.intel.com


Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>