drm/i915/pfit: Reject cloning when using pfit on ILK-BDW

drm/i915/pfit: Reject cloning when using pfit on ILK-BDW

The panel fitter lives inside the pipe and so would affect all cloned
outputs. However the relevant properties (scaling mode, TV margins)
are per-connector so we could end up with a situation where each cloned
output wants a different pfit configuration. Let's just reject pfit
usage with cloning entirely.

Currently not an issue as we don't yet expose the TV margin
properties, but if/when we add those to HDMI we could end up
in this situation. For eDP/DP we don't support cloning anyyway.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241016143134.26903-6-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>