dt-bindings:iio:magnetometer:fsl,mag3110: txt to yaml conversion

Dropped a few bits of help text in here that didn't seem to add anything
that wasn't fairly obvious.  Otherwise simple format conversion

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/20201031184854.745828-24-jic23@kernel.org