servod: servo_v4: print CC values

Add the following controls to servo v4, in order to debug PD/CCD issues:

servo_v4_chg_cc1_mv, servo_v4_chg_cc2_mv, servo_v4_dut_cc1_mv,
servo_v4_dut_cc2_mv, servo_v4_sbu1_mv, servo_v4_sbu2_mv

BUG=None
BRANCH=None
TEST=dut-control prints correct values.

Change-Id: I3da1693383c127d4a49e65bfd5eaa1d785f5e83e
Reviewed-on: https://chromium-review.googlesource.com/1503860
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
2 files changed