ath9k: Fix regression in LNA diversity

The commit "ath9k: Optimize LNA check" tried
to use the "rs_firstaggr" flag to optimize the LNA
combining algorithm when processing subframes in
an A-MPDU. This doesn't appear to work well in practice,
so revert it and use the old method of relying on
"rs_moreaggr".

Cc: stable@vger.kernel.org # 3.11
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -1269,13 +1269,6 @@ static void ath9k_antenna_check(struct ath_softc *sc,
 	if (!(ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB))
 		return;
 
-	/*
-	 * All MPDUs in an aggregate will use the same LNA
-	 * as the first MPDU.
-	 */
-	if (rs->rs_isaggr && !rs->rs_firstaggr)
-		return;
-
 	/*
 	 * Change the default rx antenna if rx diversity
 	 * chooses the other antenna 3 times in a row.