staging: iio: tsl2583: removed unused code from device probing

taos_probe() queries the all of the sensor's registers and loads all of
the values into a buffer stored on the stack. Only the chip ID register
was actually used. Change the probe function to just query the chip ID
register on the device.

Verified that the driver still functions correctly using a TSL2581
hooked up to a Raspberry Pi 2.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>