x86: config: Always scroll the display by 5 lines, for speed

Scrolling a line at a time is very slow for reasons that I don't understand.
It seems to take about 100ms to copy 4MB of RAM in the frame buffer. To cope
with this, scroll 5 lines each time.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/configs/x86-common.h

@@ -179,6 +179,7 @@
 #define VIDEO_FB_16BPP_WORD_SWAP
 #define CONFIG_I8042_KBD
 #define CONFIG_CFB_CONSOLE
+#define CONFIG_CONSOLE_SCROLL_LINES 5
 
 /*-----------------------------------------------------------------------
  * CPU Features