staging: iio: tsl2x7x: add of_match table for device tree support

Add device tree support for the tsl2x7x IIO driver with no custom
properties. The device tree documentation is in a separate commit so
that the changes to trivial-devices.txt can go in via the device
tree subsystem.

Signed-off-by: Brian Masney <masneyb@onstation.org>
CC: Rob Herring <robh+dt@kernel.org>
CC: Mark Rutland <mark.rutland@arm.com>
CC: devicetree@vger.kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>