drm/i915/gem: drop intel_display.h include

The include is not needed since commit 44a34dec ("drm/i915:
Calculate the VT-d guard size in the display code").

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/80ea203e004b7378c14f2367258b5785e40bf126.1747128495.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>