iio: magnetometer: ak8975: check if gpiod read was successful

Add a check that ensures that valid data has been read from GPIOD. If
not, log an error and return the negative read value.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
Reviewed-by: Maxwell Doose <m32285159@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: cjd8

drivers/iio/magnetometer/ak8975.c

@@ -658,6 +658,10 @@ static int wait_conversion_complete_gpio(struct ak8975_data *data,
 				 timeout_ms * USEC_PER_MSEC);
 	if (ret)
 		return ret;
+	if (val < 0) {
+		dev_err(&client->dev, "Error in reading GPIOD\n");
+		return val;
+	}
 
 	ret = i2c_smbus_read_byte_data(client, data->def->ctrl_regs[ST1]);
 	if (ret < 0)