drm/sun4i: mixer: Extend regmap max_register

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

drivers/gpu/drm/sun4i/sun8i_mixer.c

@@ -307,7 +307,7 @@ static struct regmap_config sun8i_mixer_regmap_config = {
 	.reg_bits	= 32,
 	.val_bits	= 32,
 	.reg_stride	= 4,
-	.max_register	= 0xbfffc, /* guessed */
+	.max_register	= 0xffffc, /* guessed */
 };
 
 static int sun8i_mixer_of_get_id(struct device_node *node)