nep_dmamem_alloc
sc->sc_rbring = nep_dmamem_alloc(sc, NEP_NRBDESC * sizeof(uint32_t));
sc->sc_rcring = nep_dmamem_alloc(sc, NEP_NRCDESC * sizeof(uint64_t));
sc->sc_rxmbox = nep_dmamem_alloc(sc, 64);
sc->sc_txring = nep_dmamem_alloc(sc, NEP_NTXDESC * sizeof(uint64_t));
struct nep_dmamem *nep_dmamem_alloc(struct nep_softc *, size_t);