[NET]: Add a dev_ioctl() fallback to sock_ioctl()

Currently all network protocols need to call dev_ioctl as the default
fallback in their ioctl implementations.  This patch adds a fallback
to dev_ioctl to sock_ioctl if the protocol returned -ENOIOCTLCMD.
This way all the procotol ioctl handlers can be simplified and we don't
need to export dev_ioctl.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/llc/af_llc.c

@@ -959,7 +959,7 @@ out:
 static int llc_ui_ioctl(struct socket *sock, unsigned int cmd,
 			unsigned long arg)
 {
-	return dev_ioctl(cmd, (void __user *)arg);
+	return -ENOIOCTLCMD;
 }
 
 /**