ath9k: don't strip mic on non-encrypted frames in tkip

Fix the following bug: in tkip mode, qos-null ps on/off packets
are dropped due to incorrect packet length so that ath9k softap
can't handle powersave state transition of peer STA correctly.
Signed-off-by: NMichael Liang <mliang@qca.qualcomm.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -812,6 +812,7 @@ static bool ath9k_rx_accept(struct ath_common *common,
 	is_valid_tkip = rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID &&
 		test_bit(rx_stats->rs_keyix, common->tkip_keymap);
 	strip_mic = is_valid_tkip && ieee80211_is_data(fc) &&
+		ieee80211_has_protected(fc) &&
 		!(rx_stats->rs_status &
 		(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_CRC | ATH9K_RXERR_MIC |
 		 ATH9K_RXERR_KEYMISS));