power_supply: bq25890: make chip_id int

Smatch static checker correctly detected an impossible condition because
chip_id was declared as u8, instead of int:

drivers/power/bq25890_charger.c:843 bq25890_probe()
warn: impossible condition '(bq->chip_id < 0) => (0-255 < 0)'

Also, while at it, fix the return value too.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>