drm/sun4i: mixer: Extend regmap max_register

[ Upstream commit 74ea06164cda81dc80e97790164ca533fd7e3087 ]

Better guess. Secondary CSC registers are from 0xF0000.

Signed-off-by: Martin Cerveny <m.cerveny@computer.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200906162140.5584-3-m.cerveny@computer.org


Signed-off-by: Sasha Levin <sashal@kernel.org>