drm/i915: Replace a bunch of connector->base.display_info with a local variable

Reduce the eyesore with a local variable.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1475070703-6435-10-git-send-email-ville.syrjala@linux.intel.com