[media] media:dvb:fix up ENOIOCTLCMD error handling

At commit 07d106d0, Linus pointed out that ENOIOCTLCMD should be
translated as ENOTTY to user mode.

Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>