FAFT: Adding servo functions for volume_up/down

Adding functions for tests to control pushing
the volume up and down buttons.

BUG=chromium:527484
BRANCH=none
TEST=tested on Ryu (with firmware_FastbootErase,
which is a new tests to be added)

Change-Id: I2e7cf61eede034da6f979ce8c213872121b4f605
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/301201
Reviewed-by: danny chan <dchan@chromium.org>
1 file changed