servo_v4: remove keepalive control

It's not needed since SBU detect isn't tied to PD anymore

BUG=b:128646723, chromium:942130
BRANCH=None
TEST=runs on new servo firmware, also old firmware

Change-Id: Ibfa183d5050b366b96d4535903354a02137bfc13
Reviewed-on: https://chromium-review.googlesource.com/1529842
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
2 files changed