bareudp: Convert bareudp_exit_batch_rtnl() to ->exit_rtnl().

bareudp: Convert bareudp_exit_batch_rtnl() to ->exit_rtnl().

bareudp_exit_batch_rtnl() iterates the dying netns list and performs the
same operation for each.

Let's use ->exit_rtnl().

While at it, we replace unregister_netdevice_queue() with
bareudp_dellink() for better cleanup.  It unlinks the device
from net_generic(net, bareudp_net_id)->bareudp_list, but there
is no real issue as both the dev and the list are freed later.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/20250411205258.63164-13-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>