iio:imu:mpu6050: Fixed segfault in Invensens MPU driver due to null dereference

The driver segfaults when the kernel boots with device tree as the
platform data is then not present and the pointer is deferenced without
checking it is not null.  This patch introduces such a check avoiding the
crash.
Signed-off-by: Atilla Filiz <atilla.filiz@essensium.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: Stable@vger.kernel.org

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c

@@ -660,6 +660,7 @@ static int inv_mpu_probe(struct i2c_client *client,
 {
 	struct inv_mpu6050_state *st;
 	struct iio_dev *indio_dev;
+	struct inv_mpu6050_platform_data *pdata;
 	int result;
 
 	if (!i2c_check_functionality(client->adapter,
@@ -672,8 +673,10 @@ static int inv_mpu_probe(struct i2c_client *client,
 
 	st = iio_priv(indio_dev);
 	st->client = client;
-	st->plat_data = *(struct inv_mpu6050_platform_data
+	pdata = (struct inv_mpu6050_platform_data
 			*)dev_get_platdata(&client->dev);
+	if (pdata)
+		st->plat_data = *pdata;
 	/* power is turned on inside check chip type*/
 	result = inv_check_and_setup_chip(st, id);
 	if (result)