weston-init: fix display flickering

Refer to https://secogroup.atlassian.net/browse/YT-85

 for full discussion
on this topic.

For some unknown reason, when the transparency part of "background-color"
parameter in weston.ini is lower than FF, display (both LVDS and HDMI) starts
to constantly blink if some object/sprite is moving on display.

Herewith this issue cannot be seen if application is launched in full screen
mode (e.g if seco-show-demo is running). But if seco-show-demo is stopped,
the problem immediately appears when a mouse cursor or "weston-flower" are
moved.

As digging into weston internals to understand what is going on will require
reasonable efforts, we simply changed background-color to 0xFF000000, which
also produces a black background, but which does not cause the blinking
issue to appear.

Signed-off-by: Mikhail Vanyulin <mikhail.vanyulin@rtsoft.de>

recipes-graphics/wayland/weston-init/seco-arm/weston.ini

@@ -11,7 +11,7 @@ use-pixman=false
 
 [shell]
 panel-position=none
-background-color=0x00FFFFFF
+background-color=0xFF000000
 
 [output]
 name=DPI-1