count the host rings even when they are fake
count the host rings even when they are fake

For compatibility reasons, the netmap_if always contains the
ring pointers for the host rings, even for ports that do not
support them. The new exposed fields, nr_host_tx_rings and
nr_host_rx_rings should always account for these pointers,
or the new NETMAP_RXRING will not work.

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