[PATCH] fbdev: Fix crashes in various fbdev's blank routines

The backlight changes that went in had a bug where they could cause the
kernel to access an unitialized pointer when blanking if there is no
backlight control on a machine.

The bug affects atyfb, aty128fb, nvidiafb and rivafb.  radeonfb seems to
be ok.  This fixes it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/video/aty/aty128fb.c b/drivers/video/aty/aty128fb.c
index 3e827e0..106d428 100644
--- a/drivers/video/aty/aty128fb.c
+++ b/drivers/video/aty/aty128fb.c
@@ -1800,6 +1800,9 @@
 
 static void aty128_bl_set_power(struct fb_info *info, int power)
 {
+	if (info->bl_dev == NULL)
+		return;
+
 	mutex_lock(&info->bl_mutex);
 	up(&info->bl_dev->sem);
 	info->bl_dev->props->power = power;
@@ -1828,7 +1831,7 @@
 	bd = backlight_device_register(name, par, &aty128_bl_data);
 	if (IS_ERR(bd)) {
 		info->bl_dev = NULL;
-		printk("aty128: Backlight registration failed\n");
+		printk(KERN_WARNING "aty128: Backlight registration failed\n");
 		goto error;
 	}