ath9k: Remove unused rx_edma in ath_rx_addbuffer_edma()

static void ath_rx_addbuffer_edma(struct ath_softc *sc,

				  enum ath9k_rx_qtype qtype, int size)

{

	struct ath_rx_edma *rx_edma;

	struct ath_common *common = ath9k_hw_common(sc->sc_ah);

	u32 nbuf = 0;

	rx_edma = &sc->rx.rx_edma[qtype];

	if (list_empty(&sc->rx.rxbuf)) {

		ath_print(common, ATH_DBG_QUEUE, "No free rx buf available\n");

		return;