IIO: si7020: Allocate correct amount of memory in devm_iio_device_alloc

Since only a pointer to struct i2c_client is stored in a private area
of IIO device created by the driver there's no need to allocate
sizeof(struct i2c_client) worth of storage.

Pushed to stable as this is linked to the revert patch previously.
Without this followup the original patch looks sensible.

Signed-off-by: Andrey Smirnov <[e-mail]>
Cc: [e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/humidity/si7020.c

···
 	/* Wait the maximum power-up time after software reset. */
 	msleep(15);
 
-	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*client));
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;