iio: Add channel for Phase

Add new channel type support for phase.

This channel may be used by Time-of-flight sensors to express the
phase difference between emitted and received signals. Those sensor
will then use the phase shift of return signals to approximate the
distance to objects.

Signed-off-by: Mathieu Othacehe <m.othacehe@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -86,6 +86,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_INDEX] = "index",
 	[IIO_GRAVITY]  = "gravity",
 	[IIO_POSITIONRELATIVE]  = "positionrelative",
+	[IIO_PHASE] = "phase",
 };
 
 static const char * const iio_modifier_names[] = {