staging:iio:buffering remove unused parameter dead_offset from read_last_n in all buffer implementations.

This element has been usused by the core for quite some time.  sca3000 set it none the less
until the rewrite in the previous patch (and hence didn't work).

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/staging/iio/ring_sw.c b/drivers/staging/iio/ring_sw.c
index 5fbf5ff..40beadd 100644
--- a/drivers/staging/iio/ring_sw.c
+++ b/drivers/staging/iio/ring_sw.c
@@ -139,14 +139,13 @@
 }
 
 int iio_read_first_n_sw_rb(struct iio_ring_buffer *r,
-			   size_t n, char __user *buf, int *dead_offset)
+			   size_t n, char __user *buf)
 {
 	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 
 	u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
 	u8 *data;
-	int ret, max_copied;
-	int bytes_to_rip;
+	int ret, max_copied, bytes_to_rip, dead_offset;
 
 	/* A userspace program has probably made an error if it tries to
 	 *  read something that is not a whole number of bpds.
@@ -227,9 +226,9 @@
 	current_read_p = ring->read_p;
 
 	if (initial_read_p <= current_read_p)
-		*dead_offset = current_read_p - initial_read_p;
+		dead_offset = current_read_p - initial_read_p;
 	else
-		*dead_offset = ring->buf.length*ring->buf.bytes_per_datum
+		dead_offset = ring->buf.length*ring->buf.bytes_per_datum
 			- (initial_read_p - current_read_p);
 
 	/* possible issue if the initial write has been lapped or indeed
@@ -237,7 +236,7 @@
 	/* No valid data read.
 	 * In this case the read pointer is already correct having been
 	 * pushed further than we would look. */
-	if (max_copied - *dead_offset < 0) {
+	if (max_copied - dead_offset < 0) {
 		ret = 0;
 		goto error_free_data_cpy;
 	}
@@ -253,9 +252,9 @@
 	while (ring->read_p != end_read_p)
 		ring->read_p = end_read_p;
 
-	ret = max_copied - *dead_offset;
+	ret = max_copied - dead_offset;
 
-	if (copy_to_user(buf, data + *dead_offset, ret))  {
+	if (copy_to_user(buf, data + dead_offset, ret))  {
 		ret =  -EFAULT;
 		goto error_free_data_cpy;
 	}