ath9k: Calculate ampdu limit using a helper

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index acf5372..23145ce 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -461,6 +461,7 @@
 void ath9k_btcoex_timer_resume(struct ath_softc *sc);
 void ath9k_btcoex_timer_pause(struct ath_softc *sc);
 void ath9k_btcoex_handle_interrupt(struct ath_softc *sc, u32 status);
+u16 ath9k_btcoex_aggr_limit(struct ath_softc *sc, u32 max_4ms_framelen);
 
 /********************/
 /*   LED Control    */