drm/sun4i: mixer: Convert heuristics to quirk

drm/sun4i: mixer: Convert heuristics to quirk

Determination if FCC unit can be used for VI layer alpha depends on
number of VI channels. This info won't be available anymore in future
to VI layer driver because of DE33 way of allocating planes from same
pool to different mixers.

While order is slightly changed, it doesn't affect anything due to
double buffering of registers. New order keeps related registers
together and quirk separate.

Reviewed-by: Chen-Yu Tsai <wens@kernel.org>
Tested-by: Ryan Walklin <ryan@testtoast.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://patch.msgid.link/20251104180942.61538-25-jernej.skrabec@gmail.com
Signed-off-by: Chen-Yu Tsai <wens@kernel.org>