mfd: 88pm860x: Fix possible NULL pointer dereference on i2c_new_dummy error

commit 159ce52a upstream.

During probe the driver allocates dummy I2C device for companion chip
with i2c_new_dummy() but it does not check the return value of this call.

In case of error (i2c_new_device(): memory allocation failure or I2C
address cannot be used) this function returns NULL which is later used
by regmap_init_i2c().

If i2c_new_dummy() fails for companion device, fail also the probe for
main MFD driver.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
[bwh: Backported to 3.2:
 - Adjust filename, context
 - Add kfree() before return, as driver is not using managed allocations]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/mfd/88pm860x-i2c.c

@@ -290,6 +290,12 @@ static int __devinit pm860x_probe(struct i2c_client *client,
 		chip->companion_addr = pdata->companion_addr;
 		chip->companion = i2c_new_dummy(chip->client->adapter,
 						chip->companion_addr);
+		if (!chip->companion) {
+			dev_err(&client->dev,
+				"Failed to allocate I2C companion device\n");
+			kfree(chip);
+			return -ENODEV;
+		}
 		i2c_set_clientdata(chip->companion, chip);
 	}