drm/i915: Implement connector state duplication

So that we can add connector states to the drm_atomic_state used in the
legacy modeset.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/i915/intel_crt.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_dp.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_dp_mst.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_dsi.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_dvo.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_hdmi.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_lvds.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_sdvo.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_tv.c
Simple merge