Update powerBacklightControl to support freon

Modify get_num_outputs_on() to support a freon and x
version.

BUG=chromium:413137
TEST=run power_BacklightControl on freon

Change-Id: I116408e7c4429f3713e6d9c5443cd6d71f7df13a
Reviewed-on: https://chromium-review.googlesource.com/227960
Reviewed-by: Ilja Friedel <ihf@chromium.org>
Tested-by: Ilja Friedel <ihf@chromium.org>
2 files changed