iwlwifi: move iwl_is_ht40_tx_allowed out of iwl-core.c

This is really something determined by
station parameters, so move it to
iwl-agn-sta.c.

Signed-off-by: Meenakshi Venkataraman <meenakshi.venkataraman@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.h b/drivers/net/wireless/iwlwifi/iwl-agn.h
index 3b66e30..90b1f3a 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.h
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.h
@@ -261,6 +261,9 @@
 int iwl_sta_update_ht(struct iwl_priv *priv, struct iwl_rxon_context *ctx,
 		      struct ieee80211_sta *sta);
 
+bool iwl_is_ht40_tx_allowed(struct iwl_priv *priv,
+			    struct iwl_rxon_context *ctx,
+			    struct ieee80211_sta_ht_cap *ht_cap);
 
 static inline int iwl_sta_id(struct ieee80211_sta *sta)
 {