nfp: flower: add rcu locks when accessing netdev for tunnels

nfp: flower: add rcu locks when accessing netdev for tunnels

BugLink: https://bugs.launchpad.net/bugs/1838576
[ Upstream commit cb07d915bf278a7a3938b983bbcb4921366b5eff ]

Add rcu locks when accessing netdev when processing route request
and tunnel keep alive messages received from hardware.

Fixes: 8e6a9046b66a ("nfp: flower vxlan neighbour offload")
Fixes: 856f5b135758 ("nfp: flower vxlan neighbour keep-alive")
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>