frecon: add a hook for SuspendDone DBUS signal

And use it to trigger monitor hotplug so frecon could detect monitors that
were connected or disconnected during suspend.

BUG=none
TEST=boot panther, suspend, switch monitor to other port, resume, switch to\
console using CTRL-ALT-F2

Change-Id: Ie724028ae22c801586881aaaaf9dd80e31b013d8
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/340991
6 files changed