xtensa: ISS: raise network polling rate to 10 times/sec

#define DRIVER_NAME "iss-netdev"

#define ETH_MAX_PACKET 1500

#define ETH_HEADER_OTHER 14

#define ISS_NET_TIMER_VALUE (2 * HZ)

#define ISS_NET_TIMER_VALUE (HZ / 10)

static DEFINE_SPINLOCK(opened_lock);