The CSC matrix to use depends on the output format, its range and the
colorspace.

Since we're going to add more colorspaces, let's move the CSC matrix
retrieval to a function.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20221207-rpi-hdmi-improvements-v3-7-bdd54f66884e@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>