leds: leds-lp5521: return an error code on error in probe()

If "buf" wasn't equal to LP5521_REG_R_CURR_DEFAULT the probe fails but
we still return zero.  I've changed it to print an error message and
return -EINVAL.
Reported-by: NBen Hutchings <ben@decadent.org.uk>
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NBryan Wu <cooloney@gmail.com>

drivers/leds/leds-lp5521.c

@@ -788,10 +788,17 @@ static int __devinit lp5521_probe(struct i2c_client *client,
 	 * LP5521_REG_ENABLE register will not have any effect - strange!
 	 */
 	ret = lp5521_read(client, LP5521_REG_R_CURRENT, &buf);
-	if (ret || buf != LP5521_REG_R_CURR_DEFAULT) {
+	if (ret) {
 		dev_err(&client->dev, "error in resetting chip\n");
 		goto fail2;
 	}
+	if (buf != LP5521_REG_R_CURR_DEFAULT) {
+		dev_err(&client->dev,
+			"unexpected data in register (expected 0x%x got 0x%x)\n",
+			LP5521_REG_R_CURR_DEFAULT, buf);
+		ret = -EINVAL;
+		goto fail2;
+	}
 	usleep_range(10000, 20000);
 
 	ret = lp5521_detect(client);