charger: Correctly clear manual current limit override
charger: Correctly clear manual current limit override

The official way to clear the manual current limit is to set the
override value to -1.  However, paths through the host command
CHARGE_STATE_CMD_SET_PARAM that attempt to set -1 instead select the
"nearest" current of zero.  This disables the charger instead of
disabling the manual current limit override.

BUG=chromium:870365, b:111943872
BRANCH=none
TEST=Use ectool to set and clear the current limit via
`ectool chargestate param 1 0xffffffff` on Careena clears the limit.
Signed-off-by: Jonathan Brandmeyer <fec1f53cb6eb4426eb62f1a1e49909eafbea899c@chromium.org>

Change-Id: Icfd1162300dedc2d8b7bca1c95f1ff0da6aa72a3
Reviewed-on: https://chromium-review.googlesource.com/1163983
Commit-Ready: Jonathan Brandmeyer <fec1f53cb6eb4426eb62f1a1e49909eafbea899c@chromium.org>
Tested-by: Jonathan Brandmeyer <fec1f53cb6eb4426eb62f1a1e49909eafbea899c@chromium.org>
Reviewed-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec