staging: iio: remove odd structure definition.

I've no idea where this came from!
Also fixed form -> from in comment

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Manuel Stahl <manuel.stahl@iis.fraunhofer.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/trigger.h

@@ -161,8 +161,4 @@ struct iio_trigger *iio_allocate_trigger(void);
 
 void iio_free_trigger(struct iio_trigger *trig);
 
-
-struct iio_simple_trigger {
-	struct iio_trigger trig;
-};
 #endif /* _IIO_TRIGGER_H_ */