mISDN: Fix DTMF detection enable/disable

DTMF detection was enabled when it was not supposed to.

Signed-off-by: Andreas Eversberg <andreas@eversberg.eu>
Signed-off-by: Karsten Keil <keil@b1-systems.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
3 files changed