drm/i915/icl: Configure DSI transcoder timings

As part of DSI enable sequence, transcoder timings
(horizontal & vertical) need to be set so that transcoder
will generate the stream output as per those timings.
This patch set required transcoder timings as per BSPEC.

v2: Remove TRANS_TIMING_SHIFT usage

v3 by Jani:
 - Rebase
 - Reduce temp variable use
 - Checkpatch fix

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/525949ae4e919a4f2b807d606234322534656048.1539613303.git.jani.nikula@intel.com