drm/i915/icl: Program TRANS_DDI_FUNC_CTL registers

This patch select input PIPE for DSI, data lanes width,
enable port sync mode and wait for DSI link to become ready.

v2 by Jani:
 - Use MISSING_CASE with fallthrough instead of DRM_ERROR
 - minor stylistic changes

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/080320dc9a9e321dbe73567c6a7aa1dcff0f21c2.1539613303.git.jani.nikula@intel.com