[media] s5p-jpeg: Fix encoder and decoder video dev names

It is hard to distinguish between decoder and encoder video device
because their names are same. So this patch fixes the names.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>