drm/i915/bxt: Fix BXT DSI ULPS sequence

Fix the Sequence to program BXT DSI Latch and ULPS.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1486551058-22596-6-git-send-email-vidya.srinivas@intel.com