drm/sun4i: Add CCSC property to DE2 configuration

Base addresses of channel output CSC (CCSC) depends whether mixer in
question is first or second and if it is second, if supports VEP or not.
This new property will tell which set of base addresses to take.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171201060550.10392-23-jernej.skrabec@siol.net