mac_tx_srs_ring_present
ASSERT(mac_tx_srs_ring_present(srs, desired_ring));
ASSERT(mac_tx_srs_ring_present(srs, ring));
ASSERT(mac_tx_srs_ring_present(tx_srs, ring));
extern boolean_t mac_tx_srs_ring_present(mac_soft_ring_set_t *, mac_ring_t *);