freebsd: fix bug in netmap_poll() optimization
freebsd: fix bug in netmap_poll() optimization

This bug was introduced by 968a6287512c701e1, and it only affects
select(), which uses POLLRDNORM/POLLWRNORM. The poll() syscall is
not affected by this bug, because POLLIN is used and POLLIN == 1.

Sponsored-by: Sunny Valley Networks

luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap