drm/i915/dp: add missing \n in the TPS3 debug message

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commit 06ea66b6
Author: Todd Previte <tprevite@gmail.com>
Date:   Mon Jan 20 10:19:39 2014 -0700

    drm/i915: Enable 5.4Ghz (HBR2) link rate for Displayport 1.2-capable devices

Cc: Todd Previte <tprevite@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Pimp commit message a bit.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>