CHROMIUM: drm/anx7808: Initialize video pipeline.

CHROMIUM: drm/anx7808: Initialize video pipeline.

Adds routines that initialize the video pipeline, HDMI receiver and DP
transmitter, in anx7808 chip.

BUG=chrome-os-partner:16196
TEST=With verbose logging, and HDMI cable plugged into monitor, see:
"Video resolution: 2200x1125"

On the console, do "xrandr -d :0" and see:

eDP-1 connected 1366x768+0+0 0mm x 0mm
  1366x768       59.9*+
HDMI-1 connected 1920x1080+0+768 553mm x 311mm
  1920x1080      60.0*+   50.0
  1920x1080i     30.0     25.0
  1680x1050      60.0
  1440x900       59.9
  1280x720       60.0     50.0
  720x576        50.0
  720x480        59.9
  640x480        60.0

Change-Id: I583ced0a331326e8251a18ee04157de261af7849
Signed-off-by: Jeremy Thorpe <jeremyt@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/49560