[media] exynos4-is: fimc-lite: Index out of bounds if no pixelcode found

In case no valid pixelcode is found, an i of -1 after the loop is out of
bounds for the array.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>