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

stable inclusion
from stable-5.10.9
commit 06b0d83b33b5b06e4228c56abbe32fb754813e8d
bugzilla: 47457

--------------------------------

[ Upstream commit 7887cc89 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>