dt-bindings:iio:adc:ti,ads1015 yaml conversion

This binding was moved over from hwmon some time ago so is a bit
unusual in terms of IIO bindings.  However, conversion was fairly
straight forwards.

I've listed both Dirk (who think wrote original binding) and Daniel
who added the IIO driver for this device.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20200909175946.395313-17-jic23@kernel.org