dm table: pass correct dev area size to device_area_is_valid

Incorrect device area lengths are being passed to device_area_is_valid().

The regression appeared in 2.6.31-rc1 through commit
754c5fc7ebb417b23601a6222a6005cc2e7f2913.

With the dm-stripe target, the size of the target (ti->len) was used
instead of the stripe_width (ti->len/#stripes).  An example of a
consequent incorrect error message is:

  device-mapper: table: 254:0: sdb too small for target

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 4e5b843..ebe7381 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -324,12 +324,12 @@
 	struct delay_c *dc = ti->private;
 	int ret = 0;
 
-	ret = fn(ti, dc->dev_read, dc->start_read, data);
+	ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 	if (ret)
 		goto out;
 
 	if (dc->dev_write)
-		ret = fn(ti, dc->dev_write, dc->start_write, data);
+		ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 
 out:
 	return ret;