[media] exynos-gsc: Do not swap cb/cr for semi planar formats

In the case of semi planar formats cb and cr are in the same plane
in memory, meaning that will be set to 'cb' whatever the format is,
and whatever the (packed) order of those components are.

Suggested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Thibault Saunier <thibault.saunier@osg.samsung.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>