drivers: sensor: max17055: fix TTE and TTF time units

The unit for SENSOR_CHAN_GAUGE_TIME_TO_EMPTY and
SENSOR_CHAN_GAUGE_TIME_TO_FULL are defined in
zephyr/drivers/sensor.h as being in minutes.

Change the max17055 implementation to match the API spec, fix the
annotation for time register units.

Link: https://datasheets.maximintegrated.com/en/ds/MAX17055.pdf


Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>