FB/S3C2410: check default_display parameter passed in platform data

Ensure that the default display parameter passed in via the
device's platform data is valid. It turns out when mach-bast.c
was updated, the default_display was set outside of the display
array bounds, causing a panic on startup.

If the default_display is bigger than num_displays, then generate
an error and refuse to initialise the driver.

Signed-off-by: Ben Dooks <[e-mail]>
Cc: "Antonino A. Daplas" <[e-mail]>
Cc: Vincent Sanders <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/s3c2410fb.c

···
 		return -EINVAL;
 	}
 
+	if (mach_info->default_display >= mach_info->num_displays) {
+		dev_err(&pdev->dev, "default is %d but only %d displays\n",
+			mach_info->default_display, mach_info->num_displays);
+		return -EINVAL;
+	}
+
 	display = mach_info->displays + mach_info->default_display;
 
 	irq = platform_get_irq(pdev, 0);