dt-bindings:iio:adc:mediatek,mt2701-auxadc: rename and yaml conversion.

The current driver and indeed binding are named after a part that they
do not list in the compatible.  Hence renamed the binding to reflect
one that does.

>From the driver it looks like there is a lot more backwards compatibility
than the binding currently reflects. We could consider expressing that
more explicitly in the yaml for the compatible property. I have
added one explicit pair that was present in the upstream dtsi files.

I added Matthias alongside Zhiyong Tao because I don't think
Zhiyong Tao has reviewed recent patches.  Please let me know if this
isn't the right thing to do.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Zhiyong Tao <zhiyong.tao@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20201031184854.745828-34-jic23@kernel.org