dt-bindings:iio:adc:cosmic,10001-adc yaml conversion

I don't really know much about this one, hence the binding is
a simple conversion of what was in the txt file.

Note that I have taken on maintenance of this binding as I don't
have a recent address for Phani Movva.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200909175946.395313-14-jic23@kernel.org