[media] davinci: just return 0 instead of using a var

Instead of allocating a var to store 0 and just return it,
change the code to return 0 directly.

Acked-by: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>