uboot-imx

dm: video: use constants to refer to colors

Use constants to refer to colors.
Adjust initialization of foreground and background color to avoid
setting reserved bits.
Consistently u32 instead of unsigned for color bit mask.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>