nfp: flower: move route ack control messages out of the workqueue

Previously we processed the route ack control messages in the workqueue,
this unnecessarily loads the workqueue. We can deal with these messages
sooner as we know we are going to drop them.

Fixes: 8e6a9046 ("nfp: flower vxlan neighbour offload")
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>