iio: fix opencoded for_each_set_bit()

iio_simple_dummy_trigger_h() is mostly an opencoded for_each_set_bit().
Using for_each_set_bit() make code much cleaner, and more effective.
Signed-off-by: Yury Norov <yury.norov@gmail.com>

drivers/iio/dummy/iio_simple_dummy_buffer.c

@@ -45,41 +45,31 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
 {
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
+	int i = 0, j;
 	u16 *data;
 
 	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
 	if (!data)
 		goto done;
 
-	if (!bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) {
-		/*
-		 * Three common options here:
-		 * hardware scans: certain combinations of channels make
-		 *   up a fast read.  The capture will consist of all of them.
-		 *   Hence we just call the grab data function and fill the
-		 *   buffer without processing.
-		 * software scans: can be considered to be random access
-		 *   so efficient reading is just a case of minimal bus
-		 *   transactions.
-		 * software culled hardware scans:
-		 *   occasionally a driver may process the nearest hardware
-		 *   scan to avoid storing elements that are not desired. This
-		 *   is the fiddliest option by far.
-		 * Here let's pretend we have random access. And the values are
-		 * in the constant table fakedata.
-		 */
-		int i, j;
-
-		for (i = 0, j = 0;
-		     i < bitmap_weight(indio_dev->active_scan_mask,
-				       indio_dev->masklength);
-		     i++, j++) {
-			j = find_next_bit(indio_dev->active_scan_mask,
-					  indio_dev->masklength, j);
-			/* random access read from the 'device' */
-			data[i] = fakedata[j];
-		}
-	}
+	/*
+	 * Three common options here:
+	 * hardware scans:
+	 *   certain combinations of channels make up a fast read. The capture
+	 *   will consist of all of them. Hence we just call the grab data
+	 *   function and fill the buffer without processing.
+	 * software scans:
+	 *   can be considered to be random access so efficient reading is just
+	 *   a case of minimal bus transactions.
+	 * software culled hardware scans:
+	 *   occasionally a driver may process the nearest hardware scan to avoid
+	 *   storing elements that are not desired. This is the fiddliest option
+	 *   by far.
+	 * Here let's pretend we have random access. And the values are in the
+	 * constant table fakedata.
+	 */
+	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
+		data[i++] = fakedata[j];
 
 	iio_push_to_buffers_with_timestamp(indio_dev, data,
 					   iio_get_time_ns(indio_dev));