iio: light: vcnl4000: use variables for I2C client and device instances

iio: light: vcnl4000: use variables for I2C client and device instances

After moving data->client and client->dev into variables of their own,
replace all instances of data->client and client->dev being used in
vcnl4200_init() and vcnl4000_probe() by the said variables to reduce
clutter.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Erikas Bitovtas <xerikasxx@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>