V4L/DVB (11516): drivers/media/video/saa5246a.c: fix use-after-free

I lowered the kfree(t) down a couple lines and removed the superflous
"t->vdev = NULL;"

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>