video, cfb_console: make background and foreground color configurable

make CONSOLE_BG_COL/CONSOLE_FG_COL configurable through board config file.
Clear video screen in video_init().

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Anatolij Gustschin <agust@denx.de>
diff --git a/README b/README
index f0eedbb..91c3ac0 100644
--- a/README
+++ b/README
@@ -705,6 +705,11 @@
 		the "silent" environment variable. See
 		doc/README.silent for more information.
 
+		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
+			is 0x00.
+		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
+			is 0xa0.
+
 - Console Baudrate:
 		CONFIG_BAUDRATE - in bps
 		Select one of the baudrates listed in