ath9k: allow tx99 for ar9002 based cards

As there is current support for ar9002 tx99 mode, just allow
to init debugfs and enable tx99.

Signed-off-by: Eduardo Abinader <eduardo.abinader@riverbed.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath9k/tx99.c

@@ -266,7 +266,7 @@ static const struct file_operations fops_tx99_power = {
 
 void ath9k_tx99_init_debug(struct ath_softc *sc)
 {
-	if (!AR_SREV_9300_20_OR_LATER(sc->sc_ah))
+	if (!AR_SREV_9280_20_OR_LATER(sc->sc_ah))
 		return;
 
 	debugfs_create_file("tx99", S_IRUSR | S_IWUSR,