samus: add i2c retries to backlight control
samus: add i2c retries to backlight control

Add i2c retries to backlight control. Also check return value,
if i2c transfer fails, do not continue.

Also modified backlight control so that we only send I2C commands
when backlight chip is enabled (in S0 and lid is open).

BUG=chrome-os-partner:36803
BRANCH=samus
TEST=test suspend/resume and booting and make sure panel always
comes up.

Change-Id: I0dd71c12d0c3f64a08fb389c37f64b1b0ac16fb8
Signed-off-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/250670
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
(cherry picked from commit 279e2c6386e24dbbe8d9d8ad83556f065b4b1a20)
Reviewed-on: https://chromium-review.googlesource.com/251407

thehobn/ec,thehobn/ec,thehobn/ec,thehobn/ec