gigaset: correct clearing of at_state strings on RING

In RING handling, clear the table of received parameter strings in
a loop like everywhere else, instead of by enumeration which had
already gotten out of sync.

Impact: minor bugfix
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Acked-by: Karsten Keil <keil@b1-systems.de>
CC: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/gigaset/ev-layer.c

@@ -1258,14 +1258,10 @@ static void do_action(int action, struct cardstate *cs,
 		 * note that bcs may be NULL if no B channel is free
 		 */
 		at_state2->ConState = 700;
-		kfree(at_state2->str_var[STR_NMBR]);
-		at_state2->str_var[STR_NMBR] = NULL;
-		kfree(at_state2->str_var[STR_ZCPN]);
-		at_state2->str_var[STR_ZCPN] = NULL;
-		kfree(at_state2->str_var[STR_ZBC]);
-		at_state2->str_var[STR_ZBC] = NULL;
-		kfree(at_state2->str_var[STR_ZHLC]);
-		at_state2->str_var[STR_ZHLC] = NULL;
+		for (i = 0; i < STR_NUM; ++i) {
+			kfree(at_state2->str_var[i]);
+			at_state2->str_var[i] = NULL;
+		}
 		at_state2->int_var[VAR_ZCTP] = -1;
 
 		spin_lock_irqsave(&cs->lock, flags);