[RFC] drm/exynos: improve pixel format handling

[Tobias Jakobi]

Hello,

this is an attempt to somewhat improve the handling for supported
pixel formats in the Exynos DRM. Currently DRM planes are always
created with XRGB8888, ARGB8888 and NV12 as supported formats,
even though the formats depend on the 'consumer' (mixer, FIMD,
video processor, etc.).

This series is based on the remaining patches of this series:
http://www.spinics.net/lists/linux-samsung-soc/msg43103.html

With best wishes,
Tobias