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-crypt.c b/drivers/md/dm-crypt.c
index 529e2ba..ed10381 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1318,7 +1318,7 @@
 {
 	struct crypt_config *cc = ti->private;
 
-	return fn(ti, cc->dev, cc->start, data);
+	return fn(ti, cc->dev, cc->start, ti->len, data);
 }
 
 static struct target_type crypt_target = {