drm/sun4i: frontend: Configure and enable YUV to RGB CSC when needed

In prevision of adding support for YUV formats, set the YUV to RGB
colorspace conversion coefficients if required and don't bypass the
CSC engine when converting.

The BT601 coefficients from the A33 BSP are copied over from the backend
code. Because of module inter-dependency, we can't have the frontend use
these coefficients from the backend directly.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-8-paul.kocialkowski@bootlin.com