video: Check for valid FB pointer before clearing

This command will start erasing at memory address zero
if there is not a valid framebuffer address that was found
during video_init().

This is a common case with Chrome OS devices in normal mode
when we do not execute the video option rom in coreboot.

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/cfb_console.c b/drivers/video/cfb_console.c
index 9388859..26f673a 100644
--- a/drivers/video/cfb_console.c
+++ b/drivers/video/cfb_console.c
@@ -2293,6 +2293,8 @@
 
 void video_clear(void)
 {
+	if (!video_fb_address)
+		return;
 #ifdef VIDEO_HW_RECTFILL
 	video_hw_rectfill(VIDEO_PIXEL_SIZE,	/* bytes per pixel */
 			  0,			/* dest pos x */