power: supply: max17040: remove non-working POWER_SUPPLY_PROP_STATUS

The driver was reporting POWER_SUPPLY_PROP_STATUS via platform data
functions.  Without platform data, the max17040_get_status() functions
returns early with POWER_SUPPLY_STATUS_UNKNOWN.  Since there are no
platforms using the driver with platform data (no board files with the
driver), the status property was always unknown.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>