nfp: move nfp_net_vecs_init()

Move nfp_net_vecs_init() after all datapath functions.  We will need
to init poll() callbacks from this function soon.

No functional changes.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>