[media] exynos-gsc: Add support for NV{16,21,61}M pixel formats

Those are useful formats that should be handled.

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>