dt-bindings:iio:light:ti,opt3001: txt to yaml conversion

Straight forward format conversion of this simple binding.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Andreas Dannenberg <dannenberg@ti.com>
Link: https://lore.kernel.org/r/20201031184854.745828-19-jic23@kernel.org