The hardware can count statistics and the driver has already retrieved
them via qlnx_get_counter().
Advertise the IFCAP_HWSTATS capability so that the net stack will not
double count IFCOUNTER_IBYTES.
Note that on retrieving IFCOUNTER_IBYTES the count statistics stored
in netif->if_counters[IFCOUNTER_IBYTES] is ignored so this change will
not fix anything but is only a micro optimization.
MFC after: 1 week