udp_tunnel: remove rtnl_lock dependency

udp_tunnel: remove rtnl_lock dependency

Drivers that are using ops lock and don't depend on RTNL lock
still need to manage it because udp_tunnel's RTNL dependency.
Introduce new udp_tunnel_nic_lock and use it instead of
rtnl_lock. Drop non-UDP_TUNNEL_NIC_INFO_MAY_SLEEP mode from
udp_tunnel infra (udp_tunnel_nic_device_sync_work needs to
grab udp_tunnel_nic_lock mutex and might sleep).

Cover more places in v4:

- netlink
  - udp_tunnel_notify_add_rx_port (ndo_open)
    - triggers udp_tunnel_nic_device_sync_work
  - udp_tunnel_notify_del_rx_port (ndo_stop)
    - triggers udp_tunnel_nic_device_sync_work
  - udp_tunnel_get_rx_info (__netdev_update_features)
    - triggers NETDEV_UDP_TUNNEL_PUSH_INFO
  - udp_tunnel_drop_rx_info (__netdev_update_features)
    - triggers NETDEV_UDP_TUNNEL_DROP_INFO
  - udp_tunnel_nic_reset_ntf (ndo_open)

- notifiers
  - udp_tunnel_nic_netdevice_event, depending on the event:
    - triggers NETDEV_UDP_TUNNEL_PUSH_INFO
    - triggers NETDEV_UDP_TUNNEL_DROP_INFO

- ethnl_tunnel_info_reply_size
- udp_tunnel_nic_set_port_priv (two intel drivers)

Cc: Michael Chan <michael.chan@broadcom.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Stanislav Fomichev <stfomichev@gmail.com>
Link: https://patch.msgid.link/20250616162117.287806-4-stfomichev@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>