drm/i915/chv: Remove DPIO force latency causing interpair skew issue

Latest version of the "CHV DPIO programming notes" no longer requires writes
to TX DW 11 to fix a +2UI interpair skew issue. The current code from
April 2014 was actually causing additional skew issues between all
TMDS pairs.

ver2: added same treatment to intel_dp.c based on Ville's testing.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>