[media] technisat-usb2: Don't use a deprecated call

drivers/media/dvb/dvb-usb/technisat-usb2.c: In function ‘technisat_usb2_disconnect’:
drivers/media/dvb/dvb-usb/technisat-usb2.c:770: warning: ‘cancel_rearming_delayed_work’ is deprecated (declared at include/linux/workqueue.h:421)

Cc: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>