[media] s5p-mfc: remove unnecessary check in try_fmt

We don't need to request the sizeimage or num_planes
in try_fmt.

Signed-off-by: ayaka <ayaka@soulik.info>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>