isdn: Push down BKL into ioctl functions

Push down bkl into isdn ioctl functions

[fweisbec: dropped drivers/isdn/divert/divert_procfs.c
as it has been pushed down in procfs branch already]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>