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 <[e-mail]>
Reported-by: Dan Carpenter <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/bq25890_charger.c

···
 	struct regmap *rmap;
 	struct regmap_field *rmap_fields[F_MAX_FIELDS];
 
-	u8 chip_id;
+	int chip_id;
 	struct bq25890_init_data init_data;
 	struct bq25890_state state;
 
···
 	bq->chip_id = bq25890_field_read(bq, F_PN);
 	if (bq->chip_id < 0) {
 		dev_err(dev, "Cannot read chip ID.\n");
-		return ret;
+		return bq->chip_id;
 	}
 
 	if (bq->chip_id != BQ25890_ID) {