nfp: don't try to register XDP rxq structures on control queues

Some RX rings are used for control messages, those will not have
a netdev pointer in dp.  Skip XDP rxq handling on those rings.

Fixes: 7f1c684a

 ("nfp: setup xdp_rxq_info")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>