monitor_reconfig: Disable LCD when using external monitor.

This makes us disable the internal display when it would
otherwise show just a portion of the total screen.  (This
happens when the external display supports a high enough
resolution that we assume it's a monitor rather than a
projector, and choose to use its maximum resolution.)

BUG=chromium-os:7567
TEST=updated

Review URL: http://codereview.chromium.org/3709001
3 files changed