drm/sun4i: Move the BT.601 CSC coefficients to the frontend

Both the backend and the frontend need the BT.601 CSC coefficients for
YUV to RGB conversion. Since the backend has a dependency on the
frontend (and not the other way round), move the coefficients there
so that both can access them without having to duplicate them.

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/20190118145133.21281-7-paul.kocialkowski@bootlin.com