hdctools: servo: Modify ec.py to match new battery info message

EC command 'battery' has been modified to reduce code size, and thus
retrieving battery voltage and current info in EC driver fails. Let's
modify EC driver to match its new console output.

BUG=chrome-os-partner:9188
TEST='dut-control ppvar_vbat_ma ppvar_vbat_mw ppvar_vbat_mv' works.

Change-Id: I56171f96feee0f8ec11b54165e592196328e52c2
Reviewed-on: https://gerrit.chromium.org/gerrit/23826
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
Commit-Ready: Vic Yang <victoryang@chromium.org>
Tested-by: Vic Yang <victoryang@chromium.org>
1 file changed