can: fix ioctl function removal

Commit 60649d4e

 ("can: remove obsolete empty ioctl() handler") replaced the
almost empty can_ioctl() function with sock_no_ioctl() which always returns
-EOPNOTSUPP.

Even though we don't have any ioctl() functions on socket/network layer we need
to return -ENOIOCTLCMD to be able to forward ioctl commands like SIOCGIFINDEX
to the network driver layer.

This patch fixes the wrong return codes in the CAN network layer protocols.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Fixes: 60649d4e

 ("can: remove obsolete empty ioctl() handler")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>