ath9k: Fix tx throughput drops for AR9003 chips with AES encryption

While sending aggregated frames in AES, the AR5416 chips
required additional padding b/w subframes. This workaround
is not needed for edma (AR9003 family) chips. With this patch
~4Mbps thoughput improvement was observed in clear environment.

Cc: stable@kernel.org
Signed-off-by: NRajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -671,7 +671,8 @@ static int ath_compute_num_delims(struct ath_softc *sc, struct ath_atx_tid *tid,
 	 * TODO - this could be improved to be dependent on the rate.
 	 *      The hardware can keep up at lower rates, but not higher rates
 	 */
-	if (fi->keyix != ATH9K_TXKEYIX_INVALID)
+	if ((fi->keyix != ATH9K_TXKEYIX_INVALID) &&
+	    !(sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA))
 		ndelim += ATH_AGGR_ENCRYPTDELIM;
 
 	/*