hwmon: (ads1015) Fix out-of-bounds array access

Current code uses data_rate as array index in ads1015_read_adc() and uses pga
as array index in ads1015_reg_to_mv, so we must make sure both data_rate and
pga settings are in valid value range.
Return -EINVAL if the setting is out-of-range.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

(cherry picked from commit e9814295)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

drivers/hwmon/ads1015.c

@@ -198,6 +198,7 @@ static int ads1015_get_channels_config_of(struct i2c_client *client)
 				dev_err(&client->dev,
 					"invalid gain on %s\n",
 					node->full_name);
+				return -EINVAL;
 			}
 		}
 
@@ -208,6 +209,7 @@ static int ads1015_get_channels_config_of(struct i2c_client *client)
 				dev_err(&client->dev,
 					"invalid data_rate on %s\n",
 					node->full_name);
+				return -EINVAL;
 			}
 		}