pps: timestamp is always passed to dcd_change()

Remove the code that gatheres timestamp in pps_tty_dcd_change() in case
passed ts parameter is NULL because it never happens in the current code.
Fix comments as well.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 763e061..ff7dc08 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -104,7 +104,7 @@
  *			struct pps_event_time *ts)
  *
  *	Tells the discipline that the DCD pin has changed its status and
- *	the relative timestamp. Pointer ts can be NULL.
+ *	the relative timestamp. Pointer ts cannot be NULL.
  */
 
 #include <linux/fs.h>