drm/exynos: gsc: Fix support for NV16/61, YUV420/YVU420 and YUV422 modes

Fix following issues related to planar YUV pixel format configuration:
- NV16/61 modes were incorrectly programmed as NV12/21,
- YVU420 was programmed as YUV420 on source,
- YVU420 and YUV422 were programmed as YUV420 on output.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>