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/include/video_fb.h b/include/video_fb.h
index 028e2a6..6cd4e37 100644
--- a/include/video_fb.h
+++ b/include/video_fb.h
@@ -18,8 +18,13 @@
 #ifndef _VIDEO_FB_H_
 #define _VIDEO_FB_H_
 
+#if defined(CONFIG_SYS_CONSOLE_FG_COL) && defined(CONFIG_SYS_CONSOLE_BG_COL)
+#define CONSOLE_BG_COL            CONFIG_SYS_CONSOLE_BG_COL
+#define CONSOLE_FG_COL            CONFIG_SYS_CONSOLE_FG_COL
+#else
 #define CONSOLE_BG_COL            0x00
 #define CONSOLE_FG_COL            0xa0
+#endif
 
 /*
  * Graphic Data Format (GDF) bits for VIDEO_DATA_FORMAT