nfp: update maintainer

Take over maintainership of the nfp driver from Simon as he
is moving away from Corigine.

Signed-off-by: Louis Peens <louis.peens@corigine.com>
Acked-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>