staging: iio: dummy: fix compile error when not using buffering

Commit 4ae03019 ("staging:iio:dummy: Register same channels for
device and buffer") has changed the number of parameters for
iio_simple_dummy_configure_buffer() only for the IIO_SIMPLE_DUMMY_BUFFER
case.  Fix this by also changing the placeholder function declared in
the header when buffering is not enabled.
Signed-off-by: Vlad Dogaru <vlad.dogaru@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/iio_simple_dummy.h

@@ -117,8 +117,7 @@ enum iio_simple_dummy_scan_elements {
 int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev);
 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev);
 #else
-static inline int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *channels, unsigned int num_channels)
+static inline int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 {
 	return 0;
 };