drm/panel: ld9040: Use better magic values

drm/panel: ld9040: Use better magic values

I have no idea what the prior magic values mean, and I have no idea
what my replacement (extracted from [1]) magic values mean.

What I do know, is that these new values result in a much better
picture, where the blacks are really black (as you would expect on an
AMOLED display) instead of grey-ish.

[1]: https://github.com/dorimanx/Dorimanx-SG2-I9100-Kernel/blob/master-jelly-bean/arch/arm/mach-exynos/u1-panel.h

v2: Remove spurious new line

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230708084027.18352-2-paul@crapouillou.net