staging: iio: ring_sw remove unnecessary function stub.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/ring_sw.h

@@ -220,8 +220,6 @@ void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time);
 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s);
 
 #else /* CONFIG_IIO_RING_BUFFER*/
-static inline void iio_ring_sw_register_funcs(struct iio_ring_access_funcs *ra)
-{};
 struct iio_sw_ring_helper_state {
 	struct iio_dev			*indio_dev;
 };