ARM: dts: ux500/golden: Set display max brightness

A too high brightness by default (default is max) makes the
screen go blank. Set this to 15 as in the Vendor tree.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20201214223413.253893-1-linus.walleij@linaro.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/ste-ux500-samsung-golden.dts

@@ -326,6 +326,7 @@ dsi-controller@a0351000 {
 				panel@0 {
 					compatible = "samsung,s6e63m0";
 					reg = <0>;
+					max-brightness = <15>;
 					vdd3-supply = <&panel_reg_3v0>;
 					vci-supply = <&panel_reg_1v8>;
 					reset-gpios = <&gpio4 11 GPIO_ACTIVE_LOW>;