dt-bindings:iio:magnetometer:pni,rm3100: txt to yaml conversion.

Simple binding format conversion.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Song Qiang <songqiang1304521@gmail.com>
Link: https://lore.kernel.org/r/20201031184854.745828-28-jic23@kernel.org