pacina: Fix single bipolar measurements for PAC1954

Correctly pass polarity information to both the
_read_voltage() & _read_current().

BUG=None
TEST=Tested on CPDC using external SMU

Change-Id: Ia5368003a60bff42508113c30e62a9bb9cf3067b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/4555059
Reviewed-by: Sam McNally <sammc@chromium.org>
Tested-by: Louis Jung <ljung@google.com>
Reviewed-by: Ben Drayton <bendrayton@google.com>
Commit-Queue: Louis Jung <ljung@google.com>
1 file changed