Error handling code in usbtv_probe() misses usb_put_dev().

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>