drm/i915: Remove unused loop from intel_dp_mst_compute_config

drm/i915: Remove unused loop from intel_dp_mst_compute_config

Now that conn_state is passed in as argument to compute_config, it's
guaranteed that there is a connector for the argument. The code that
looks for the connector is now dead, and completely unused. Delete it.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470755054-32699-8-git-send-email-maarten.lankhorst@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>