fb: add hooks to handle KDB enter/exit

Add fb ops to handle enter/exit of the kernel debugger.  If present, the
fb core will register them with KGDB and they'll be called when the
debugger is entered and exited.  The new functions are responsible for
switching to an appropriate debug framebuffer and restoring the
interrupted state at exit time.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
diff --git a/drivers/video/console/fbcon.h b/drivers/video/console/fbcon.h
index 89a34688..6bd2e0c 100644
--- a/drivers/video/console/fbcon.h
+++ b/drivers/video/console/fbcon.h
@@ -74,6 +74,7 @@
 	int    cursor_reset;
 	int    blank_state;
 	int    graphics;
+	int    save_graphics; /* for debug enter/leave */
 	int    flags;
 	int    rotate;
 	int    cur_rotate;