dm delay: document that offsets are specified in sectors

Only delay params are mentioned in delay.txt.
Mention offsets just like documents for linear and flakey do.
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Documentation/device-mapper/delay.txt

@@ -8,6 +8,7 @@ Parameters:
     <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 
 With separate write parameters, the first set is only used for reads.
+Offsets are specified in sectors.
 Delays are specified in milliseconds.
 
 Example scripts

drivers/md/dm-delay.c

@@ -122,6 +122,7 @@ static void flush_expired_bios(struct work_struct *work)
  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
  *
  * With separate write parameters, the first set is only used for reads.
+ * Offsets are specified in sectors.
  * Delays are specified in milliseconds.
  */
 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)