Revert "can: fix handling of unmodifiable configuration options fix"

This reverts commit ded1c127 which was
bce271f2 upstream.

It was applied incorrectly, and isn't needed for 3.12-stable.
Reported-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

drivers/net/can/dev.c

@@ -644,9 +644,6 @@ static int can_changelink(struct net_device *dev,
 	/* We need synchronization with dev->stop() */
 	ASSERT_RTNL();
 
-	if (!data)
-		return 0;
-
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm;