nfp: mark port state as stale if update failed

If reading new state of the port failed, mark the port back as CHANGED.
This way next user state request will trigger refresh, which will
hopefully succeed.

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