can: fix oops caused by wrong rtnl dellink usage

commit 25e1ed6e64f52a692ba3191c4fde650aab3ecc07 upstream.

For 'real' hardware CAN devices the netlink interface is used to set CAN
specific communication parameters. Real CAN hardware can not be created nor
removed with the ip tool ...

This patch adds a private dellink function for the CAN device driver interface
that does just nothing.

It's a follow up to commit 993e6f2f ("can: fix oops caused by wrong rtnl
newlink usage") but for dellink.

Reported-by: ajneu <ajneu1@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>