staging: iio: resolver: ad2s1210: add phase lock range support

The AD2S1210 chip has a phase lock range feature that allows selecting
the allowable phase difference between the excitation output and the
sine and cosine inputs. This can be set to either 44 degrees (default)
or 360 degrees.

This patch adds a new phase channel with a phase0_mag_rising event that
can be used to configure the phase lock range. Actually emitting the
event will be added in a subsequent patch.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-5-ec00746840fc@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>