drm/vc4: hdmi: Add a CSC setup callback

drm/vc4: hdmi: Add a CSC setup callback

Similarly to the previous patches, the CSC setup is slightly different in
the BCM2711 than in the previous generations. Let's add a callback for it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/5c19bbf10153cb42ca0fb67e08606c8295c17236.1599120059.git-series.maxime@cerno.tech