nfp: Remove switchdev.h inclusion

This is no longer necessary after a5084bb7

 ("nfp: Implement
ndo_get_port_parent_id()")

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>