isdn: hisax: Fix lock imbalance.

Add omittted unlocks to 2 functions.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Karsten Keil <Karsten-Keil@t-online.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>